🐐 Tests

README.md

@@ -24,7 +24,7 @@ Variable can consist of lower-case letters, numbers, as well as `_`.
 
 ### Compound assignment
 
-`AVGE` (+=) and `MINVE` (-=) are shorthand for incrementing or decrementing a variable:
+`AVGE` (+=), `MINVE` (-=), `MVLTIPLICA` (*=) and `DIVIDE` (/=) are shorthand for updating a variable with an arithmetic operation:
 
 ![Compound assignment](snippets/compound.png)
 
@@ -32,7 +32,7 @@ Variable can consist of lower-case letters, numbers, as well as `_`.
 > VIII
 ```
 
-`x AVGE III` is equivalent to `DESIGNA x VT x + III`.
+`x AVGE III` is equivalent to `DESIGNA x VT x + III`; `MINVE`, `MVLTIPLICA` and `DIVIDE` expand the same way with subtraction, multiplication and division.
 
 ### Destructuring
 
@@ -74,15 +74,19 @@ Single-quoted strings do **not** interpolate — `'{nomen}'` is the literal text
 
 Strings support the same indexing and slicing syntax as arrays. Indexing is 1-based and returns a single-character string:
 
+![String indexing](snippets/string_index.png)
+
 ```
-"SALVTE"[I]             @> "S"
-"SALVTE"[III]           @> "L"
+> S
+> L
 ```
 
 Slicing uses `VSQVE` with inclusive bounds, returning a substring:
 
+![String slicing](snippets/string_slice.png)
+
 ```
-"SALVTE"[II VSQVE IV]   @> "ALV"
+> ALV
 ```
 
 Integer modulo is `RELIQVVM`: `VII RELIQVVM III` evaluates to `I`. Under the `FRACTIO` module it returns a fraction, so `IIIS RELIQVVM IS` is `S` (i.e. 1/2).
@@ -138,10 +142,7 @@ Individual elements can be accessed by index using square brackets. Indexing is
 
 Arrays are concatenated with `@`:
 
-```
-DESIGNA x VT [I, II, III] @ [IV, V]
-DIC x
-```
+![Array concatenation](snippets/array_concat.png)
 
 ```
 > [I, II, III, IV, V]
@@ -182,7 +183,7 @@ If-then statements are denoted with the keywords `SI` (if) and `TVNC` (then). Th
 Will return `I` (1), as the conditional evaluates `x` to be true.
 
 ### Boolean expressions
-In conditionals, `EST` functions as an equality evaluation, `DISPAR` as not-equal, and `MINVS` (<) and `PLVS` (>) function as inequality evaluation.
+In conditionals, `EST` functions as an equality evaluation, `DISPAR` as not-equal, and `MINVS` (<), `PLVS` (>), `HAVD_PLVS` (≤), and `HAVD_MINVS` (≥) function as inequality evaluation.
 
 ### ALIVD
 
@@ -221,6 +222,16 @@ The keyword `ET` can be used as a boolean "and". The keyword `AVT` can be used a
 > LV
 ```
 
+An optional `GRADV` clause sets the stride. The step must be a nonzero
+integer expression; positive values ascend, negative values descend, and
+the endpoint is included only when the stride lands on it exactly.
+
+![DONICVM with GRADV](snippets/donicvm_gradv.png)
+
+```
+> XXV
+```
+
 ### DVM loops
 
 ![DVM loop](snippets/dvm.png)
@@ -255,11 +266,7 @@ condition. Exit the loop with `ERVMPE` (or `REDI` from inside a function).
 
 Variables can be unpacked in `PER` loops, similar to `DESIGNA` destructuring:
 
-```
-PER a, b IN [[I, II], [III, IV]] FAC {
-  DIC(a + b)
-}
-```
+![PER destructuring](snippets/per_destructure.png)
 
 ```
 > III
@@ -270,13 +277,7 @@ PER a, b IN [[I, II], [III, IV]] FAC {
 
 Errors can be caught using `TEMPTA` (temptare = to try) and `CAPE` (capere = to catch). The `CAPE` block binds the error message to a variable as a string.
 
-```
-TEMPTA {
-  DESIGNA x VT I / NVLLVS
-} CAPE error {
-  DIC(error)
-}
-```
+![TEMPTA / CAPE](snippets/tempta_cape.png)
 
 ```
 > Division by zero
@@ -375,6 +376,11 @@ Parses a Roman numeral string and returns its integer value. The argument must b
 
 Returns the type of `value` as a string: `NVMERVS` (integer), `LITTERA` (string), `VERAX` (boolean), `CATALOGVS` (list), `FRACTIO` (fraction), `TABVLA` (dict), `FVNCTIO` (function), or `NVLLVS` (null).
 
+### LITTERA
+`LITTERA(value)`
+
+Returns `value` formatted as the same display string `DIC` would print. Integers become Roman numerals (zero becomes `NVLLVS`), fractions use the `S`/`:`/`.`/`|` notation, booleans become `VERITAS`/`FALSITAS`, arrays are space-separated in brackets, and dicts use the `{ key VT value, ... }` form. Strings pass through unchanged. Respects `MAGNVM` and `SVBNVLLA` for large and negative numbers. Inverse of `NVMERVS` for integers: `NVMERVS(LITTERA(n)) == n`.
+
 ### DORMI
 `DORMI(n)`
 
@@ -395,6 +401,16 @@ Replaces all non-overlapping matches of the regex `pattern` in `string` with `re
 
 Splits `string` by `delimiter` and returns an array of substrings. Both arguments must be strings. If the delimiter is not found, returns a single-element array containing the original string. If the delimiter is an empty string, splits into individual characters.
 
+### MAIVSCVLA
+`MAIVSCVLA(string)`
+
+Returns a new string with every ASCII letter `a`–`z` replaced by its uppercase counterpart `A`–`Z`. All other bytes (digits, punctuation, non-ASCII) pass through unchanged.
+
+### MINVSCVLA
+`MINVSCVLA(string)`
+
+Returns a new string with every ASCII letter `A`–`Z` replaced by its lowercase counterpart `a`–`z`. All other bytes (digits, punctuation, non-ASCII) pass through unchanged.
+
 ## Modules
 Modules are additions to the base `CENTVRION` syntax. They add or change certain features. Modules are included in your code by having
 

centvrion/ast_nodes.py

@@ -64,6 +64,8 @@ OP_STR = {
   "KEYWORD_EST": "EST", "KEYWORD_DISPAR": "DISPAR",
   "KEYWORD_MINVS": "MINVS",
   "KEYWORD_PLVS": "PLVS", "KEYWORD_ET": "ET", "KEYWORD_AVT": "AVT",
+  "KEYWORD_HAVD_PLVS": "HAVD_PLVS",
+  "KEYWORD_HAVD_MINVS": "HAVD_MINVS",
 }
 
 def single_num_to_int(i, m):
@@ -367,19 +369,28 @@ class DataArray(Node):
 
 
 class DataRangeArray(Node):
-  def __init__(self, from_value, to_value) -> None:
+  def __init__(self, from_value, to_value, step=None) -> None:
     self.from_value = from_value
     self.to_value = to_value
+    self.step = step
 
   def __eq__(self, other):
-    return type(self) == type(other) and self.from_value == other.from_value and self.to_value == other.to_value
+    return (type(self) == type(other)
+            and self.from_value == other.from_value
+            and self.to_value == other.to_value
+            and self.step == other.step)
 
   def __repr__(self) -> str:
-    content_string = rep_join([self.from_value, self.to_value])
-    return f"RangeArray([{content_string}])"
+    parts = [self.from_value, self.to_value]
+    if self.step is not None:
+      parts.append(self.step)
+    return f"RangeArray([{rep_join(parts)}])"
 
   def print(self):
-    return f"[{self.from_value.print()} VSQVE {self.to_value.print()}]"
+    base = f"[{self.from_value.print()} VSQVE {self.to_value.print()}"
+    if self.step is not None:
+      base += f" GRADV {self.step.print()}"
+    return base + "]"
 
   def _eval(self, vtable):
     vtable, from_val = self.from_value.eval(vtable)
@@ -388,7 +399,25 @@ class DataRangeArray(Node):
       raise CentvrionError("Range bounds must be numbers")
     from_int = from_val.value() or 0
     to_int = to_val.value() or 0
-    return vtable, ValList([ValInt(i) for i in range(from_int, to_int + 1)])
+    if self.step is None:
+      return vtable, ValList([ValInt(i) for i in range(from_int, to_int + 1)])
+    vtable, step_val = self.step.eval(vtable)
+    if not isinstance(step_val, ValInt):
+      raise CentvrionError("Range step must be a number")
+    step_int = step_val.value()
+    if step_int == 0:
+      raise CentvrionError("Range step cannot be zero")
+    items = []
+    i = from_int
+    if step_int > 0:
+      while i <= to_int:
+        items.append(ValInt(i))
+        i += step_int
+    else:
+      while i >= to_int:
+        items.append(ValInt(i))
+        i += step_int
+    return vtable, ValList(items)
 
 
 class DataDict(Node):
@@ -937,6 +966,14 @@ class BinOp(Node):
         if isinstance(lv, (str, list)) or isinstance(rv, (str, list)):
           raise CentvrionError("Cannot compare strings or arrays with PLVS")
         return vtable, ValBool((lv or 0) > (rv or 0))
+      case "KEYWORD_HAVD_PLVS":
+        if isinstance(lv, (str, list)) or isinstance(rv, (str, list)):
+          raise CentvrionError("Cannot compare strings or arrays with HAVD_PLVS")
+        return vtable, ValBool((lv or 0) <= (rv or 0))
+      case "KEYWORD_HAVD_MINVS":
+        if isinstance(lv, (str, list)) or isinstance(rv, (str, list)):
+          raise CentvrionError("Cannot compare strings or arrays with HAVD_MINVS")
+        return vtable, ValBool((lv or 0) >= (rv or 0))
       case "KEYWORD_EST":
         if ((isinstance(left, ValInt) and lv == 0 and isinstance(right, ValNul)) or
             (isinstance(left, ValNul) and isinstance(right, ValInt) and rv == 0)):
@@ -1431,6 +1468,26 @@ class BuiltIn(Node):
         if isinstance(params[0], (ValList, ValStr, ValDict)):
           return vtable, ValInt(len(params[0].value()))
         raise CentvrionError("LONGITVDO requires an array, string, or dict")
+      case "LITTERA":
+        if len(params) != 1:
+          raise CentvrionError("LITTERA takes exactly I argument")
+        return vtable, ValStr(make_string(params[0], magnvm, svbnvlla))
+      case "MAIVSCVLA":
+        if len(params) != 1:
+          raise CentvrionError("MAIVSCVLA takes exactly I argument")
+        val = params[0]
+        if not isinstance(val, ValStr):
+          raise CentvrionError(f"MAIVSCVLA expects a string, got {type(val).__name__}")
+        s = val.value()
+        return vtable, ValStr("".join(chr(ord(c) - 32) if "a" <= c <= "z" else c for c in s))
+      case "MINVSCVLA":
+        if len(params) != 1:
+          raise CentvrionError("MINVSCVLA takes exactly I argument")
+        val = params[0]
+        if not isinstance(val, ValStr):
+          raise CentvrionError(f"MINVSCVLA expects a string, got {type(val).__name__}")
+        s = val.value()
+        return vtable, ValStr("".join(chr(ord(c) + 32) if "A" <= c <= "Z" else c for c in s))
       case "CLAVES":
         if not isinstance(params[0], ValDict):
           raise CentvrionError("CLAVES requires a dict")

centvrion/compiler/emit_expr.py

@@ -19,6 +19,8 @@ _BINOP_FN = {
   "KEYWORD_DISPAR":   "cent_neq",
   "KEYWORD_MINVS":    "cent_lt",
   "KEYWORD_PLVS":     "cent_gt",
+  "KEYWORD_HAVD_PLVS":  "cent_lte",
+  "KEYWORD_HAVD_MINVS": "cent_gte",
   "KEYWORD_ET":       "cent_and",
   "KEYWORD_AVT":      "cent_or",
 }
@@ -127,7 +129,7 @@ def emit_expr(node, ctx):
   if isinstance(node, UnaryMinus):
     inner_lines, inner_var = emit_expr(node.expr, ctx)
     tmp = ctx.fresh_tmp()
-    return inner_lines + [f"CentValue {tmp} = cent_int(-{inner_var}.ival);"], tmp
+    return inner_lines + [f"CentValue {tmp} = cent_neg({inner_var});"], tmp
 
   if isinstance(node, UnaryNot):
     inner_lines, inner_var = emit_expr(node.expr, ctx)
@@ -164,10 +166,21 @@ def emit_expr(node, ctx):
     hi_lines, hi_var = emit_expr(node.to_value, ctx)
     tmp = ctx.fresh_tmp()
     i_var = ctx.fresh_tmp()
-    cap = f"({hi_var}.ival >= {lo_var}.ival ? (int)({hi_var}.ival - {lo_var}.ival + 1) : 0)"
-    lines = lo_lines + hi_lines + [
-      f"CentValue {tmp} = cent_list_new({cap});",
-      f"for (long {i_var} = {lo_var}.ival; {i_var} <= {hi_var}.ival; {i_var}++) {{",
+    if node.step is None:
+      cap = f"({hi_var}.ival >= {lo_var}.ival ? (int)({hi_var}.ival - {lo_var}.ival + 1) : 0)"
+      lines = lo_lines + hi_lines + [
+        f"CentValue {tmp} = cent_list_new({cap});",
+        f"for (long {i_var} = {lo_var}.ival; {i_var} <= {hi_var}.ival; {i_var}++) {{",
+        f"  cent_list_push(&{tmp}, cent_int({i_var}));",
+        "}",
+      ]
+      return lines, tmp
+    step_lines, step_var = emit_expr(node.step, ctx)
+    lines = lo_lines + hi_lines + step_lines + [
+      f'if ({step_var}.type != CENT_INT) cent_type_error("Range step must be a number");',
+      f'if ({step_var}.ival == 0) cent_runtime_error("Range step cannot be zero");',
+      f"CentValue {tmp} = cent_list_new(0);",
+      f"for (long {i_var} = {lo_var}.ival; ({step_var}.ival > 0 ? {i_var} <= {hi_var}.ival : {i_var} >= {hi_var}.ival); {i_var} += {step_var}.ival) {{",
       f"  cent_list_push(&{tmp}, cent_int({i_var}));",
       "}",
     ]
@@ -235,6 +248,23 @@ def _emit_builtin(node, ctx):
     case "LONGITVDO":
       lines.append(f"CentValue {tmp} = cent_longitudo({param_vars[0]});")
 
+    case "LITTERA":
+      lines.append(f"CentValue {tmp} = cent_littera({param_vars[0]});")
+
+    case "MAIVSCVLA":
+      if len(param_vars) != 1:
+        lines.append(f'cent_runtime_error("MAIVSCVLA takes exactly I argument");')
+        lines.append(f"CentValue {tmp} = cent_null();")
+      else:
+        lines.append(f"CentValue {tmp} = cent_maivscvla({param_vars[0]});")
+
+    case "MINVSCVLA":
+      if len(param_vars) != 1:
+        lines.append(f'cent_runtime_error("MINVSCVLA takes exactly I argument");')
+        lines.append(f"CentValue {tmp} = cent_null();")
+      else:
+        lines.append(f"CentValue {tmp} = cent_minvscvla({param_vars[0]});")
+
     case "FORTVITVS_NVMERVS":
       if not ctx.has_module("FORS"):
         lines.append('cent_runtime_error("FORS module required for FORTVITVS_NVMERVS");')

centvrion/compiler/emitter.py

@@ -92,6 +92,8 @@ def compile_program(program):
   lines.append("  cent_init();")
   if "MAGNVM" in ctx.modules:
     lines.append("  cent_magnvm = 1;")
+  if "SVBNVLLA" in ctx.modules:
+    lines.append("  cent_svbnvlla = 1;")
   lines.append("  CentScope _scope = {0};")
   lines.append("  CentValue _return_val = cent_null();")
 

centvrion/compiler/runtime/cent_runtime.c

@@ -15,6 +15,7 @@
 
 CentArena *cent_arena;
 int cent_magnvm = 0;
+int cent_svbnvlla = 0;
 
 /* ------------------------------------------------------------------ */
 /* Portable xorshift32 RNG (matches Python _CentRng)                   */
@@ -181,7 +182,15 @@ void cent_int_to_roman(long n, char *buf, size_t bufsz) {
     if (bufsz > 6) { memcpy(buf, "NVLLVS", 6); buf[6] = '\0'; }
     return;
   }
-  if (n < 0 || (n > 3999 && !cent_magnvm))
+  if (n < 0) {
+    if (!cent_svbnvlla)
+      cent_runtime_error("number out of range for Roman numerals");
+    if (bufsz < 2) cent_runtime_error("Roman numeral buffer overflow");
+    buf[0] = '-';
+    cent_int_to_roman(-n, buf + 1, bufsz - 1);
+    return;
+  }
+  if (n > 3999 && !cent_magnvm)
     cent_runtime_error("number out of range for Roman numerals");
   size_t pos = 0;
   if (n > 3999) {
@@ -271,8 +280,13 @@ static int write_val(CentValue v, char *buf, int bufsz) {
     case CENT_FRAC: {
       long num = v.fval.num, den = v.fval.den;
       if (den < 0) { num = -num; den = -den; }
-      if (num < 0)
-        cent_runtime_error("cannot display negative numbers without SVBNVLLA");
+      int negative = 0;
+      if (num < 0) {
+        if (!cent_svbnvlla)
+          cent_runtime_error("cannot display negative numbers without SVBNVLLA");
+        negative = 1;
+        num = -num;
+      }
       long int_part = num / den;
       long rem_num  = num % den;
 
@@ -297,11 +311,13 @@ static int write_val(CentValue v, char *buf, int bufsz) {
         for (int i = 0; i < (int)((level_int % 6) % 2); i++) frac_buf[frac_pos++] = '.';
       }
 
-      n = int_len + frac_pos;
+      n = int_len + frac_pos + (negative ? 1 : 0);
       if (buf && n < bufsz) {
-        memcpy(buf, int_buf, int_len);
-        memcpy(buf + int_len, frac_buf, frac_pos);
-        buf[n] = '\0';
+        int pos = 0;
+        if (negative) buf[pos++] = '-';
+        memcpy(buf + pos, int_buf, int_len); pos += int_len;
+        memcpy(buf + pos, frac_buf, frac_pos); pos += frac_pos;
+        buf[pos] = '\0';
       }
       return n;
     }
@@ -391,6 +407,13 @@ static void to_frac(CentValue v, long *num, long *den) {
   else                     { *num = v.fval.num; *den = v.fval.den; }
 }
 
+CentValue cent_neg(CentValue v) {
+  if (v.type == CENT_INT)  return cent_int(-v.ival);
+  if (v.type == CENT_FRAC) return frac_reduce(-v.fval.num, v.fval.den);
+  cent_type_error("Unary minus requires a number");
+  return cent_null();
+}
+
 CentValue cent_add(CentValue a, CentValue b) {
   if (a.type == CENT_INT && b.type == CENT_INT)
     return cent_int(a.ival + b.ival);
@@ -564,6 +587,28 @@ CentValue cent_gt(CentValue a, CentValue b) {
   return cent_null();
 }
 
+CentValue cent_lte(CentValue a, CentValue b) {
+  if ((a.type == CENT_INT || a.type == CENT_FRAC || a.type == CENT_NULL) &&
+      (b.type == CENT_INT || b.type == CENT_FRAC || b.type == CENT_NULL)) {
+    long an, ad, bn, bd;
+    to_frac(a, &an, &ad); to_frac(b, &bn, &bd);
+    return cent_bool(an * bd <= bn * ad);
+  }
+  cent_type_error("'HAVD_PLVS' requires two integers");
+  return cent_null();
+}
+
+CentValue cent_gte(CentValue a, CentValue b) {
+  if ((a.type == CENT_INT || a.type == CENT_FRAC || a.type == CENT_NULL) &&
+      (b.type == CENT_INT || b.type == CENT_FRAC || b.type == CENT_NULL)) {
+    long an, ad, bn, bd;
+    to_frac(a, &an, &ad); to_frac(b, &bn, &bd);
+    return cent_bool(an * bd >= bn * ad);
+  }
+  cent_type_error("'HAVD_MINVS' requires two integers");
+  return cent_null();
+}
+
 CentValue cent_and(CentValue a, CentValue b) {
   if (a.type != CENT_BOOL || b.type != CENT_BOOL)
     cent_type_error("'ET' requires two booleans");
@@ -622,6 +667,34 @@ CentValue cent_longitudo(CentValue v) {
   return cent_null(); /* unreachable; silences warning */
 }
 
+CentValue cent_littera(CentValue v) {
+  return cent_str(cent_make_string(v));
+}
+
+CentValue cent_maivscvla(CentValue v) {
+  if (v.type != CENT_STR) cent_type_error("'MAIVSCVLA' requires a string");
+  size_t len = strlen(v.sval);
+  char *out = cent_arena_alloc(cent_arena, len + 1);
+  for (size_t i = 0; i < len; i++) {
+    unsigned char c = (unsigned char)v.sval[i];
+    out[i] = (c >= 'a' && c <= 'z') ? (char)(c - ('a' - 'A')) : (char)c;
+  }
+  out[len] = '\0';
+  return cent_str(out);
+}
+
+CentValue cent_minvscvla(CentValue v) {
+  if (v.type != CENT_STR) cent_type_error("'MINVSCVLA' requires a string");
+  size_t len = strlen(v.sval);
+  char *out = cent_arena_alloc(cent_arena, len + 1);
+  for (size_t i = 0; i < len; i++) {
+    unsigned char c = (unsigned char)v.sval[i];
+    out[i] = (c >= 'A' && c <= 'Z') ? (char)(c + ('a' - 'A')) : (char)c;
+  }
+  out[len] = '\0';
+  return cent_str(out);
+}
+
 CentValue cent_typvs(CentValue v) {
   switch (v.type) {
     case CENT_INT:  return cent_str("NVMERVS");

centvrion/compiler/runtime/cent_runtime.h

@@ -97,6 +97,9 @@ extern CentArena *cent_arena;
 /* Set to 1 when CVM MAGNVM is active; enables extended numeral display */
 extern int cent_magnvm;
 
+/* Set to 1 when CVM SVBNVLLA is active; enables negative number display */
+extern int cent_svbnvlla;
+
 /* ------------------------------------------------------------------ */
 /* Value constructors                                                   */
 /* ------------------------------------------------------------------ */
@@ -197,6 +200,7 @@ char *cent_make_string(CentValue v);
 /* Arithmetic and comparison operators                                  */
 /* ------------------------------------------------------------------ */
 
+CentValue cent_neg(CentValue v);               /* unary minus: INT or FRAC */
 CentValue cent_add(CentValue a, CentValue b);  /* INT+INT or FRAC+FRAC/INT */
 CentValue cent_array_concat(CentValue a, CentValue b); /* @ operator: concatenate two arrays */
 CentValue cent_concat(CentValue a, CentValue b); /* & operator: coerce all types to str */
@@ -210,6 +214,8 @@ CentValue cent_eq (CentValue a, CentValue b);  /* EST  → BOOL         */
 CentValue cent_neq(CentValue a, CentValue b);  /* DISPAR → BOOL       */
 CentValue cent_lt (CentValue a, CentValue b);  /* MINVS → BOOL        */
 CentValue cent_gt (CentValue a, CentValue b);  /* PLVS  → BOOL        */
+CentValue cent_lte(CentValue a, CentValue b);  /* HAVD_PLVS  → BOOL   */
+CentValue cent_gte(CentValue a, CentValue b);  /* HAVD_MINVS → BOOL   */
 CentValue cent_and(CentValue a, CentValue b);  /* ET    → BOOL        */
 CentValue cent_or (CentValue a, CentValue b);  /* AVT   → BOOL        */
 
@@ -221,6 +227,9 @@ void      cent_dic(CentValue v);                              /* DIC */
 CentValue cent_avdi(void);                                     /* AVDI */
 CentValue cent_avdi_numerus(void);                    /* AVDI_NVMERVS */
 CentValue cent_longitudo(CentValue v);                  /* LONGITVDO  */
+CentValue cent_littera(CentValue v);                            /* LITTERA */
+CentValue cent_maivscvla(CentValue v);                          /* MAIVSCVLA */
+CentValue cent_minvscvla(CentValue v);                          /* MINVSCVLA */
 CentValue cent_fortuitus_numerus(CentValue lo, CentValue hi); /* FORTVITVS_NVMERVS */
 CentValue cent_fortuita_electionis(CentValue lst);          /* FORTVITA_ELECTIO */
 CentValue cent_decimatio(CentValue lst);                       /* DECIMATIO */

centvrion/lexer.py

@@ -11,6 +11,7 @@ keyword_tokens = [("KEYWORD_"+i, i) for i in [
   "DEFINI",
   "DESIGNA",
   "DISPAR",
+  "DIVIDE",
   "DONICVM",
   "DVM",
   "CONTINVA",
@@ -20,10 +21,14 @@ keyword_tokens = [("KEYWORD_"+i, i) for i in [
   "FAC",
   "FALSITAS",
   "FVNCTIO",
+  "GRADV",
+  "HAVD_MINVS",
+  "HAVD_PLVS",
   "INVOCA",
   "IN",
   "MINVE",
   "MINVS",
+  "MVLTIPLICA",
   "NON",
   "NVLLVS",
   "PER",
@@ -50,7 +55,10 @@ builtin_tokens = [("BUILTIN", i) for i in [
   "EVERRE",
   "FORTVITVS_NVMERVS",
   "FORTVITA_ELECTIO",
+  "LITTERA",
   "LONGITVDO",
+  "MAIVSCVLA",
+  "MINVSCVLA",
   "NVMERVS",
   "ORDINA",
   "SEMEN",
@@ -103,8 +111,8 @@ whitespace_tokens = [
 ]
 
 all_tokens = (
-  keyword_tokens +
   builtin_tokens +
+  keyword_tokens +
   module_tokens +
   data_tokens +
   symbol_tokens +

centvrion/parser.py

@@ -115,7 +115,8 @@ class Parser():
       precedence=[
         ('left', ["KEYWORD_AVT"]),
         ('left', ["KEYWORD_ET"]),
-        ('left', ["KEYWORD_PLVS", "KEYWORD_MINVS", "KEYWORD_EST", "KEYWORD_DISPAR"]),
+        ('left', ["KEYWORD_PLVS", "KEYWORD_MINVS", "KEYWORD_EST", "KEYWORD_DISPAR",
+                  "KEYWORD_HAVD_PLVS", "KEYWORD_HAVD_MINVS"]),
         ('left', ["SYMBOL_AMPERSAND", "SYMBOL_AT", "SYMBOL_PLUS", "SYMBOL_MINUS"]),
         ('left', ["SYMBOL_TIMES", "SYMBOL_DIVIDE", "KEYWORD_RELIQVVM"]),
         ('right', ["UMINUS", "UNOT"]),
@@ -197,6 +198,14 @@ class Parser():
     def statement_minve(tokens):
       return ast_nodes.Designa(tokens[0], ast_nodes.BinOp(tokens[0], tokens[2], "SYMBOL_MINUS"))
 
+    @self.pg.production('statement : id KEYWORD_MVLTIPLICA expression')
+    def statement_mvltiplica(tokens):
+      return ast_nodes.Designa(tokens[0], ast_nodes.BinOp(tokens[0], tokens[2], "SYMBOL_TIMES"))
+
+    @self.pg.production('statement : id KEYWORD_DIVIDE expression')
+    def statement_divide(tokens):
+      return ast_nodes.Designa(tokens[0], ast_nodes.BinOp(tokens[0], tokens[2], "SYMBOL_DIVIDE"))
+
     @self.pg.production('statement : expression')
     def statement_expression(tokens):
       return ast_nodes.ExpressionStatement(tokens[0])
@@ -267,6 +276,11 @@ class Parser():
       range_array = ast_nodes.DataRangeArray(tokens[3], tokens[5])
       return ast_nodes.PerStatement(range_array, tokens[1], tokens[8])
 
+    @self.pg.production('donicum_statement : KEYWORD_DONICVM id KEYWORD_VT expression KEYWORD_VSQVE expression KEYWORD_GRADV expression KEYWORD_FAC SYMBOL_LCURL statements SYMBOL_RCURL')
+    def donicum_step(tokens):
+      range_array = ast_nodes.DataRangeArray(tokens[3], tokens[5], tokens[7])
+      return ast_nodes.PerStatement(range_array, tokens[1], tokens[10])
+
     # expressions
     @self.pg.production('expressions : SYMBOL_LPARENS expression_list')
     def expressions(tokens):
@@ -334,6 +348,8 @@ class Parser():
     @self.pg.production('expression : expression KEYWORD_DISPAR expression')
     @self.pg.production('expression : expression KEYWORD_MINVS expression')
     @self.pg.production('expression : expression KEYWORD_PLVS expression')
+    @self.pg.production('expression : expression KEYWORD_HAVD_PLVS expression')
+    @self.pg.production('expression : expression KEYWORD_HAVD_MINVS expression')
     @self.pg.production('expression : expression KEYWORD_ET expression')
     @self.pg.production('expression : expression KEYWORD_AVT expression')
     def binop(tokens):
@@ -383,6 +399,10 @@ class Parser():
     def range_array(tokens):
       return ast_nodes.DataRangeArray(tokens[1], tokens[3])
 
+    @self.pg.production('expression : SYMBOL_LBRACKET expression KEYWORD_VSQVE expression KEYWORD_GRADV expression SYMBOL_RBRACKET')
+    def range_array_step(tokens):
+      return ast_nodes.DataRangeArray(tokens[1], tokens[3], tokens[5])
+
     @self.pg.production('expression : expression SYMBOL_LBRACKET expression SYMBOL_RBRACKET', precedence='INDEX')
     def array_index(tokens):
       return ast_nodes.ArrayIndex(tokens[0], tokens[2])

language/main.tex

@@ -33,13 +33,15 @@
         \languageline{statement}{\texttt{DESIGNA} \textbf{id} \texttt{,} \textit{ids} \texttt{VT} \textit{expression}} \\
         \languageline{statement}{\textbf{id} \texttt{AVGE} \textit{expression}} \\
         \languageline{statement}{\textbf{id} \texttt{MINVE} \textit{expression}} \\
+        \languageline{statement}{\textbf{id} \texttt{MVLTIPLICA} \textit{expression}} \\
+        \languageline{statement}{\textbf{id} \texttt{DIVIDE} \textit{expression}} \\
         \languageline{statement}{\texttt{DEFINI} \textbf{id} \texttt{(} \textit{optional-ids} \texttt{)} \texttt{VT} \textit{scope}} \\
         \languageline{statement}{\textit{if-statement}} \\
         \languageline{statement}{\texttt{DVM} \textit{expression} \texttt{FAC} \textit{scope}} \\
         \languageline{statement}{\texttt{AETERNVM} \texttt{FAC} \textit{scope}} \\
         \languageline{statement}{\texttt{PER} \textbf{id} \texttt{IN} \textit{expression} \texttt{FAC} \textit{scope}} \\
         \languageline{statement}{\texttt{PER} \textbf{id}\texttt{,} \textbf{id-list} \texttt{IN} \textit{expression} \texttt{FAC} \textit{scope}} \\
-        \languageline{statement}{\texttt{DONICVM} \textbf{id} \texttt{VT} \textit{expression} \texttt{VSQVE} \textit{expression} \texttt{FAC} \textit{scope}} \\
+        \languageline{statement}{\texttt{DONICVM} \textbf{id} \texttt{VT} \textit{expression} \texttt{VSQVE} \textit{expression} \textit{optional-step} \texttt{FAC} \textit{scope}} \\
         \languageline{statement}{\texttt{REDI(} \textit{optional-expressions} \texttt{)}} \\
         \languageline{statement}{\texttt{ERVMPE}} \\
         \languageline{statement}{\texttt{CONTINVA}} \\
@@ -71,7 +73,7 @@
         \languageline{literal}{\textbf{numeral}} \\
         \languageline{literal}{\textbf{bool}} \\
         \languageline{literal}{\texttt{[} \textit{optional-expressions} \texttt{]}} \\
-        \languageline{literal}{\texttt{[} \textit{expression} \texttt{VSQVE} \textit{expression} \texttt{]} \textnormal{\small\ (inclusive on both ends)}} \\
+        \languageline{literal}{\texttt{[} \textit{expression} \texttt{VSQVE} \textit{expression} \textit{optional-step} \texttt{]} \textnormal{\small\ (inclusive on both ends)}} \\
         \languageline{literal}{\texttt{TABVLA} \texttt{\{} \textit{optional-dict-items} \texttt{\}}} \\ \hline
 
         \languageline{optional-dict-items}{\textit{dict-items}} \\
@@ -92,6 +94,9 @@
 
         \languageline{expressions}{\textit{expression}, \textit{expressions}} \\
         \languageline{expressions}{\textit{expression}} \\ \hline
+
+        \languageline{optional-step}{\texttt{GRADV} \textit{expression}} \\
+        \languageline{optional-step}{} \\ \hline
     \end{tabular}
   \end{center}
 \end{table}
@@ -106,7 +111,7 @@
   \item \textbf{interpolated-string}: \\ A double-quoted string containing \texttt{\{}\textit{expression}\texttt{\}} segments. Each expression is evaluated and coerced to a string. Use \texttt{\{\{} and \texttt{\}\}} for literal braces.
   \item \textbf{numeral}: \\ Roman numerals consisting of the uppercase characters I, V, X, L, C, D, and M. Can also include underscore if the module MAGNVM.
   \item \textbf{bool}: \\ VERITAS or FALSITAS.
-  \item \textbf{binop}: \\ Binary operators: \texttt{+}, \texttt{-}, \texttt{*}, \texttt{/}, \texttt{RELIQVVM} (modulo), \texttt{EST} (equality), \texttt{DISPAR} (not-equal), \texttt{MINVS} (<), \texttt{PLVS} (>), \texttt{ET} (and), \texttt{AVT} (or), \texttt{\&} (string concatenation), \texttt{@} (array concatenation).
+  \item \textbf{binop}: \\ Binary operators: \texttt{+}, \texttt{-}, \texttt{*}, \texttt{/}, \texttt{RELIQVVM} (modulo), \texttt{EST} (equality), \texttt{DISPAR} (not-equal), \texttt{MINVS} (<), \texttt{PLVS} (>), \texttt{HAVD\_PLVS} ($\leq$), \texttt{HAVD\_MINVS} ($\geq$), \texttt{ET} (and), \texttt{AVT} (or), \texttt{\&} (string concatenation), \texttt{@} (array concatenation).
   \item \textbf{unop}: \\ Unary operators: \texttt{-} (negation), \texttt{NON} (boolean not).
 \end{itemize}
 

pyproject.toml

@@ -0,0 +1,3 @@
+[tool.pytest.ini_options]
+python_files = ["[0-9][0-9]_test_*.py", "test_*.py"]
+testpaths = ["tests"]

snippets/array_concat.cent

@@ -0,0 +1,2 @@
+DESIGNA x VT [I, II, III] @ [IV, V]
+DIC(x)

snippets/compound.cent

@@ -1,3 +1,6 @@
 DESIGNA x VT V
 x AVGE III
+x MINVE II
+x MVLTIPLICA IV
+x DIVIDE III
 DIC(x)

snippets/donicvm_gradv.cent

@@ -0,0 +1,5 @@
+DESIGNA s VT NVLLVS
+DONICVM i VT I VSQVE X GRADV II FAC {
+  s AVGE i
+}
+DIC(s)

snippets/littera.cent

@@ -0,0 +1,3 @@
+DESIGNA n VT VII
+DESIGNA s VT LITTERA(n) & " est septem"
+DIC(s)

snippets/per_destructure.cent

@@ -0,0 +1,3 @@
+PER a, b IN [[I, II], [III, IV]] FAC {
+  DIC(a + b)
+}

snippets/string_index.cent

@@ -0,0 +1,2 @@
+DIC("SALVTE"[I])
+DIC("SALVTE"[III])

snippets/string_slice.cent

@@ -0,0 +1 @@
+DIC("SALVTE"[II VSQVE IV])

snippets/syntaxes/centvrion.sublime-syntax

@@ -70,7 +70,7 @@ contexts:
       scope: constant.language.centvrion
 
   builtins:
-    - match: '\b(ADIVNGE|AVDI_NVMERVS|AVDI|AVSCVLTA|CLAVES|DECIMATIO|DIC|DORMI|EVERRE|FORTVITVS_NVMERVS|FORTVITA_ELECTIO|LEGE|LONGITVDO|NVMERVS|ORDINA|PETE|PETITVR|QVAERE|SCINDE|SCRIBE|SEMEN|SENATVS|SVBSTITVE|TYPVS)\b'
+    - match: '\b(ADIVNGE|AVDI_NVMERVS|AVDI|AVSCVLTA|CLAVES|DECIMATIO|DIC|DORMI|EVERRE|FORTVITVS_NVMERVS|FORTVITA_ELECTIO|LEGE|LITTERA|LONGITVDO|MAIVSCVLA|MINVSCVLA|NVMERVS|ORDINA|PETE|PETITVR|QVAERE|SCINDE|SCRIBE|SEMEN|SENATVS|SVBSTITVE|TYPVS)\b'
       scope: support.function.builtin.centvrion
 
   modules:
@@ -78,7 +78,7 @@ contexts:
       scope: support.class.module.centvrion
 
   keywords:
-    - match: '\b(AETERNVM|ALIVD|AVGE|AVT|CAPE|CONTINVA|DEFINI|DESIGNA|DISPAR|DONICVM|DVM|ERVMPE|EST|ET|FAC|FVNCTIO|INVOCA|IN|MINVE|MINVS|NON|PER|PLVS|REDI|RELIQVVM|SI|TABVLA|TEMPTA|TVNC|VSQVE|VT|CVM)\b'
+    - match: '\b(HAVD_PLVS|HAVD_MINVS|AETERNVM|ALIVD|AVGE|AVT|CAPE|CONTINVA|DEFINI|DESIGNA|DISPAR|DIVIDE|DONICVM|DVM|ERVMPE|EST|ET|FAC|FVNCTIO|GRADV|INVOCA|IN|MINVE|MINVS|MVLTIPLICA|NON|PER|PLVS|REDI|RELIQVVM|SI|TABVLA|TEMPTA|TVNC|VSQVE|VT|CVM)\b'
       scope: keyword.control.centvrion
 
   operators:

snippets/tempta_cape.cent

@@ -0,0 +1,5 @@
+TEMPTA {
+  DESIGNA x VT I / NVLLVS
+} CAPE error {
+  DIC(error)
+}

tests/01_test_core____.py

@@ -0,0 +1,450 @@
+from tests._helpers import (
+  unittest, parameterized, Fraction, time,
+  run_test, run_compiler_error_test,
+  ArrayIndex, ArraySlice, Bool, BinOp, BuiltIn, DataArray, DataDict, DataRangeArray,
+  Defini, Continva, Designa, DesignaDestructure, DesignaIndex, DumStatement,
+  Erumpe, ExpressionStatement, Fvnctio, ID, InterpolatedString, Invoca,
+  ModuleCall, Nullus, Numeral, PerStatement, Program, Redi, SiStatement,
+  String, TemptaStatement, UnaryMinus, UnaryNot, Fractio, frac_to_fraction,
+  fraction_to_frac, num_to_int, int_to_num, make_string,
+  ValInt, ValStr, ValBool, ValList, ValDict, ValNul, ValFunc, ValFrac,
+  CentvrionError, _RUNTIME_C, _cent_rng,
+  Lexer, Parser, compile_program,
+  os, subprocess, tempfile, StringIO, patch,
+)
+
+
+# --- Output ---
+
+output_tests = [
+  ("DIC(\"hello\")", Program([], [ExpressionStatement(BuiltIn("DIC", [String("hello")]))]), ValStr("hello"), "hello\n"),
+  ("DIC(\"world\")", Program([], [ExpressionStatement(BuiltIn("DIC", [String("world")]))]), ValStr("world"), "world\n"),
+  ("DIC(III)", Program([], [ExpressionStatement(BuiltIn("DIC", [Numeral("III")]))]), ValStr("III"), "III\n"),
+  ("DIC(X)", Program([], [ExpressionStatement(BuiltIn("DIC", [Numeral("X")]))]), ValStr("X"), "X\n"),
+  ("DIC(MMXXV)", Program([], [ExpressionStatement(BuiltIn("DIC", [Numeral("MMXXV")]))]), ValStr("MMXXV"), "MMXXV\n"),
+  ("DIC('hello')", Program([], [ExpressionStatement(BuiltIn("DIC", [String("hello")]))]), ValStr("hello"), "hello\n"),
+  ("DIC('world')", Program([], [ExpressionStatement(BuiltIn("DIC", [String("world")]))]), ValStr("world"), "world\n"),
+  ("DIC(\"a\", \"b\")", Program([], [ExpressionStatement(BuiltIn("DIC", [String("a"), String("b")]))]), ValStr("a b"), "a b\n"),
+  ("DIC(\"line one\")\nDIC(\"line two\")", Program([], [ExpressionStatement(BuiltIn("DIC", [String("line one")])), ExpressionStatement(BuiltIn("DIC", [String("line two")]))]), ValStr("line two"), "line one\nline two\n"),
+  ("DIC(DIC(II))", Program([], [ExpressionStatement(BuiltIn("DIC", [BuiltIn("DIC", [Numeral("II")])]))]), ValStr("II"), "II\nII\n"),
+  ("EVERRE()", Program([], [ExpressionStatement(BuiltIn("EVERRE", []))]), ValNul(), "\033[2J\033[H"),
+]
+
+class TestOutput(unittest.TestCase):
+  @parameterized.expand(output_tests)
+  def test_output(self, source, nodes, value, output):
+    run_test(self, source, nodes, value, output)
+
+# --- Arithmetic ---
+
+arithmetic_tests = [
+  ("I + I", Program([], [ExpressionStatement(BinOp(Numeral("I"), Numeral("I"), "SYMBOL_PLUS"))]), ValInt(2)),
+  ("X - III", Program([], [ExpressionStatement(BinOp(Numeral("X"), Numeral("III"), "SYMBOL_MINUS"))]), ValInt(7)),
+  ("III * IV", Program([], [ExpressionStatement(BinOp(Numeral("III"), Numeral("IV"), "SYMBOL_TIMES"))]), ValInt(12)),
+  ("X / II", Program([], [ExpressionStatement(BinOp(Numeral("X"), Numeral("II"), "SYMBOL_DIVIDE"))]), ValInt(5)),
+  ("X / III", Program([], [ExpressionStatement(BinOp(Numeral("X"), Numeral("III"), "SYMBOL_DIVIDE"))]), ValInt(3)),           # integer division: 10 // 3 = 3
+  ("X RELIQVVM III", Program([], [ExpressionStatement(BinOp(Numeral("X"), Numeral("III"), "KEYWORD_RELIQVVM"))]), ValInt(1)),  # 10 % 3 = 1
+  ("IX RELIQVVM III", Program([], [ExpressionStatement(BinOp(Numeral("IX"), Numeral("III"), "KEYWORD_RELIQVVM"))]), ValInt(0)), # exact divisor
+  ("VII RELIQVVM X", Program([], [ExpressionStatement(BinOp(Numeral("VII"), Numeral("X"), "KEYWORD_RELIQVVM"))]), ValInt(7)),   # dividend < divisor
+  ("II + III * IV", Program([], [ExpressionStatement(BinOp(Numeral("II"), BinOp(Numeral("III"), Numeral("IV"), "SYMBOL_TIMES"), "SYMBOL_PLUS"))]), ValInt(14)),    # precedence: 2 + (3*4) = 14
+  ("(II + III) * IV", Program([], [ExpressionStatement(BinOp(BinOp(Numeral("II"), Numeral("III"), "SYMBOL_PLUS"), Numeral("IV"), "SYMBOL_TIMES"))]), ValInt(20)),  # parens: (2+3)*4 = 20
+  ("CVM SVBNVLLA\n- III", Program([ModuleCall("SVBNVLLA")], [ExpressionStatement(UnaryMinus(Numeral("III")))]), ValInt(-3)),            # unary negation
+  ("CVM SVBNVLLA\n- (II + III)", Program([ModuleCall("SVBNVLLA")], [ExpressionStatement(UnaryMinus(BinOp(Numeral("II"), Numeral("III"), "SYMBOL_PLUS")))]), ValInt(-5)),     # unary negation of expression
+  ("CVM SVBNVLLA\n- - II", Program([ModuleCall("SVBNVLLA")], [ExpressionStatement(UnaryMinus(UnaryMinus(Numeral("II"))))]), ValInt(2)),            # double negation
+  ("CVM SVBNVLLA\nIII + - II", Program([ModuleCall("SVBNVLLA")], [ExpressionStatement(BinOp(Numeral("III"), UnaryMinus(Numeral("II")), "SYMBOL_PLUS"))]), ValInt(1)),        # unary in binary context
+]
+
+class TestArithmetic(unittest.TestCase):
+  @parameterized.expand(arithmetic_tests)
+  def test_arithmetic(self, source, nodes, value):
+    run_test(self, source, nodes, value)
+
+# --- Precedence and associativity ---
+#
+# Precedence (lowest → highest):
+#   AVT < ET < (EST, DISPAR, PLVS, MINVS) < (+ -) < (* / RELIQVVM) < UMINUS < INDEX
+
+precedence_tests = [
+  # * binds tighter than -: 10 - (2*3) = 4, not (10-2)*3 = 24
+  ("X - II * III",
+    Program([], [ExpressionStatement(BinOp(Numeral("X"), BinOp(Numeral("II"), Numeral("III"), "SYMBOL_TIMES"), "SYMBOL_MINUS"))]),
+    ValInt(4)),
+  # / binds tighter than +: (10/2) + 3 = 8, not 10/(2+3) = 2
+  ("X / II + III",
+    Program([], [ExpressionStatement(BinOp(BinOp(Numeral("X"), Numeral("II"), "SYMBOL_DIVIDE"), Numeral("III"), "SYMBOL_PLUS"))]),
+    ValInt(8)),
+  # + binds tighter than EST: (2+3)==5 = True, not 2+(3==5) = type error
+  ("II + III EST V",
+    Program([], [ExpressionStatement(BinOp(BinOp(Numeral("II"), Numeral("III"), "SYMBOL_PLUS"), Numeral("V"), "KEYWORD_EST"))]),
+    ValBool(True)),
+  # * binds tighter than PLVS: (2*3)>4 = True
+  ("II * III PLVS IV",
+    Program([], [ExpressionStatement(BinOp(BinOp(Numeral("II"), Numeral("III"), "SYMBOL_TIMES"), Numeral("IV"), "KEYWORD_PLVS"))]),
+    ValBool(True)),
+  # comparison binds tighter than ET: (1==2) AND (2==2) = False AND True = False
+  ("I EST II ET II EST II",
+    Program([], [ExpressionStatement(BinOp(BinOp(Numeral("I"), Numeral("II"), "KEYWORD_EST"), BinOp(Numeral("II"), Numeral("II"), "KEYWORD_EST"), "KEYWORD_ET"))]),
+    ValBool(False)),
+  # + binds tighter than DISPAR: (2+3)!=5 = False, not 2+(3!=5) = type error
+  ("II + III DISPAR V",
+    Program([], [ExpressionStatement(BinOp(BinOp(Numeral("II"), Numeral("III"), "SYMBOL_PLUS"), Numeral("V"), "KEYWORD_DISPAR"))]),
+    ValBool(False)),
+  # DISPAR binds tighter than ET: (1!=2) AND (2!=2) = True AND False = False
+  ("I DISPAR II ET II DISPAR II",
+    Program([], [ExpressionStatement(BinOp(BinOp(Numeral("I"), Numeral("II"), "KEYWORD_DISPAR"), BinOp(Numeral("II"), Numeral("II"), "KEYWORD_DISPAR"), "KEYWORD_ET"))]),
+    ValBool(False)),
+  # ET binds tighter than AVT: True OR (False AND False) = True
+  ("VERITAS AVT FALSITAS ET FALSITAS",
+    Program([], [ExpressionStatement(BinOp(Bool(True), BinOp(Bool(False), Bool(False), "KEYWORD_ET"), "KEYWORD_AVT"))]),
+    ValBool(True)),
+  # UMINUS binds tighter than *: (-2)*3 = -6, not -(2*3) = -6 (same value, different tree)
+  ("CVM SVBNVLLA\n- II * III",
+    Program([ModuleCall("SVBNVLLA")], [ExpressionStatement(BinOp(UnaryMinus(Numeral("II")), Numeral("III"), "SYMBOL_TIMES"))]),
+    ValInt(-6)),
+  # UMINUS binds tighter than +: (-2)+3 = 1, not -(2+3) = -5
+  ("CVM SVBNVLLA\n- II + III",
+    Program([ModuleCall("SVBNVLLA")], [ExpressionStatement(BinOp(UnaryMinus(Numeral("II")), Numeral("III"), "SYMBOL_PLUS"))]),
+    ValInt(1)),
+  # INDEX binds tighter than UMINUS: -(arr[I]) = -1
+  ("CVM SVBNVLLA\n- [I, II, III][I]",
+    Program([ModuleCall("SVBNVLLA")], [ExpressionStatement(UnaryMinus(ArrayIndex(DataArray([Numeral("I"), Numeral("II"), Numeral("III")]), Numeral("I"))))]),
+    ValInt(-1)),
+  # INDEX binds tighter than NON: NON (arr[I]) = NON VERITAS = False
+  ("NON [VERITAS, FALSITAS][I]",
+    Program([], [ExpressionStatement(UnaryNot(ArrayIndex(DataArray([Bool(True), Bool(False)]), Numeral("I"))))]),
+    ValBool(False)),
+  # INDEX binds tighter than +: (arr[II]) + X = 2 + 10 = 12
+  ("[I, II, III][II] + X",
+    Program([], [ExpressionStatement(BinOp(ArrayIndex(DataArray([Numeral("I"), Numeral("II"), Numeral("III")]), Numeral("II")), Numeral("X"), "SYMBOL_PLUS"))]),
+    ValInt(12)),
+  # left-associativity of -: (10-3)-2 = 5, not 10-(3-2) = 9
+  ("X - III - II",
+    Program([], [ExpressionStatement(BinOp(BinOp(Numeral("X"), Numeral("III"), "SYMBOL_MINUS"), Numeral("II"), "SYMBOL_MINUS"))]),
+    ValInt(5)),
+  # left-associativity of /: (12/2)/3 = 2, not 12/(2/3) = 18
+  ("XII / II / III",
+    Program([], [ExpressionStatement(BinOp(BinOp(Numeral("XII"), Numeral("II"), "SYMBOL_DIVIDE"), Numeral("III"), "SYMBOL_DIVIDE"))]),
+    ValInt(2)),
+  # RELIQVVM same precedence as *, /; left-associative: (17 % 5) % 2 = 0
+  ("XVII RELIQVVM V RELIQVVM II",
+    Program([], [ExpressionStatement(
+      BinOp(BinOp(Numeral("XVII"), Numeral("V"), "KEYWORD_RELIQVVM"),
+            Numeral("II"), "KEYWORD_RELIQVVM"))]),
+    ValInt(0)),
+  # RELIQVVM binds tighter than +: 2 + (7 % 3) = 3, not (2+7) % 3 = 0
+  ("II + VII RELIQVVM III",
+    Program([], [ExpressionStatement(
+      BinOp(Numeral("II"),
+            BinOp(Numeral("VII"), Numeral("III"), "KEYWORD_RELIQVVM"),
+            "SYMBOL_PLUS"))]),
+    ValInt(3)),
+  # left-associativity of AVT: (False OR True) OR False = True
+  ("FALSITAS AVT VERITAS AVT FALSITAS",
+    Program([], [ExpressionStatement(BinOp(BinOp(Bool(False), Bool(True), "KEYWORD_AVT"), Bool(False), "KEYWORD_AVT"))]),
+    ValBool(True)),
+]
+
+class TestPrecedence(unittest.TestCase):
+  @parameterized.expand(precedence_tests)
+  def test_precedence(self, source, nodes, value):
+    run_test(self, source, nodes, value)
+
+# --- Assignment ---
+
+assignment_tests = [
+  ("DESIGNA x VT III\nx",
+    Program([], [Designa(ID("x"), Numeral("III")), ExpressionStatement(ID("x"))]),
+    ValInt(3)),
+  ("DESIGNA msg VT \"hello\"\nmsg",
+    Program([], [Designa(ID("msg"), String("hello")), ExpressionStatement(ID("msg"))]),
+    ValStr("hello")),
+  ("DESIGNA msg VT 'hello'\nmsg",
+    Program([], [Designa(ID("msg"), String("hello")), ExpressionStatement(ID("msg"))]),
+    ValStr("hello")),
+  ("DESIGNA a VT V\nDESIGNA b VT X\na + b",
+    Program([], [Designa(ID("a"), Numeral("V")), Designa(ID("b"), Numeral("X")),
+                 ExpressionStatement(BinOp(ID("a"), ID("b"), "SYMBOL_PLUS"))]),
+    ValInt(15)),
+  ("DESIGNA x VT II\nDESIGNA x VT x + I\nx",
+    Program([], [Designa(ID("x"), Numeral("II")),
+                 Designa(ID("x"), BinOp(ID("x"), Numeral("I"), "SYMBOL_PLUS")),
+                 ExpressionStatement(ID("x"))]),
+    ValInt(3)),
+  # Compound assignment — AVGE (+=)
+  ("DESIGNA x VT V\nx AVGE III\nx",
+    Program([], [Designa(ID("x"), Numeral("V")),
+                 Designa(ID("x"), BinOp(ID("x"), Numeral("III"), "SYMBOL_PLUS")),
+                 ExpressionStatement(ID("x"))]),
+    ValInt(8)),
+  # Compound assignment — MINVE (-=)
+  ("DESIGNA x VT X\nx MINVE III\nx",
+    Program([], [Designa(ID("x"), Numeral("X")),
+                 Designa(ID("x"), BinOp(ID("x"), Numeral("III"), "SYMBOL_MINUS")),
+                 ExpressionStatement(ID("x"))]),
+    ValInt(7)),
+  # AVGE with complex expression
+  ("DESIGNA x VT I\nx AVGE II + III\nx",
+    Program([], [Designa(ID("x"), Numeral("I")),
+                 Designa(ID("x"), BinOp(ID("x"), BinOp(Numeral("II"), Numeral("III"), "SYMBOL_PLUS"), "SYMBOL_PLUS")),
+                 ExpressionStatement(ID("x"))]),
+    ValInt(6)),
+  # AVGE inside a loop (DONICVM range is inclusive: I VSQVE III = [1, 2, 3])
+  ("DESIGNA s VT NVLLVS\nDONICVM i VT I VSQVE III FAC {\ns AVGE i\n}\ns",
+    Program([], [Designa(ID("s"), Nullus()),
+                 PerStatement(DataRangeArray(Numeral("I"), Numeral("III")), ID("i"),
+                   [Designa(ID("s"), BinOp(ID("s"), ID("i"), "SYMBOL_PLUS"))]),
+                 ExpressionStatement(ID("s"))]),
+    ValInt(6)),
+  # Compound assignment — MVLTIPLICA (*=)
+  ("DESIGNA x VT III\nx MVLTIPLICA II\nx",
+    Program([], [Designa(ID("x"), Numeral("III")),
+                 Designa(ID("x"), BinOp(ID("x"), Numeral("II"), "SYMBOL_TIMES")),
+                 ExpressionStatement(ID("x"))]),
+    ValInt(6)),
+  # Compound assignment — DIVIDE (/=)
+  ("DESIGNA x VT XII\nx DIVIDE III\nx",
+    Program([], [Designa(ID("x"), Numeral("XII")),
+                 Designa(ID("x"), BinOp(ID("x"), Numeral("III"), "SYMBOL_DIVIDE")),
+                 ExpressionStatement(ID("x"))]),
+    ValInt(4)),
+  # MVLTIPLICA with complex RHS — whole expression is captured before the op
+  ("DESIGNA x VT II\nx MVLTIPLICA II + I\nx",
+    Program([], [Designa(ID("x"), Numeral("II")),
+                 Designa(ID("x"), BinOp(ID("x"), BinOp(Numeral("II"), Numeral("I"), "SYMBOL_PLUS"), "SYMBOL_TIMES")),
+                 ExpressionStatement(ID("x"))]),
+    ValInt(6)),
+  # DIVIDE with complex RHS
+  ("DESIGNA x VT XX\nx DIVIDE II + II\nx",
+    Program([], [Designa(ID("x"), Numeral("XX")),
+                 Designa(ID("x"), BinOp(ID("x"), BinOp(Numeral("II"), Numeral("II"), "SYMBOL_PLUS"), "SYMBOL_DIVIDE")),
+                 ExpressionStatement(ID("x"))]),
+    ValInt(5)),
+]
+
+class TestAssignment(unittest.TestCase):
+  @parameterized.expand(assignment_tests)
+  def test_assignment(self, source, nodes, value):
+    run_test(self, source, nodes, value)
+
+# --- Destructuring ---
+
+destructuring_tests = [
+  # basic: unpack multi-return function
+  (
+    "DEFINI pair (a, b) VT { REDI (a, b) }\nDESIGNA x, y VT INVOCA pair (III, VII)\nx + y",
+    Program([], [
+      Defini(ID("pair"), [ID("a"), ID("b")], [Redi([ID("a"), ID("b")])]),
+      DesignaDestructure([ID("x"), ID("y")], Invoca(ID("pair"), [Numeral("III"), Numeral("VII")])),
+      ExpressionStatement(BinOp(ID("x"), ID("y"), "SYMBOL_PLUS")),
+    ]),
+    ValInt(10),
+  ),
+  # unpack array literal
+  (
+    "DESIGNA a, b VT [I, II]\na + b",
+    Program([], [
+      DesignaDestructure([ID("a"), ID("b")], DataArray([Numeral("I"), Numeral("II")])),
+      ExpressionStatement(BinOp(ID("a"), ID("b"), "SYMBOL_PLUS")),
+    ]),
+    ValInt(3),
+  ),
+  # three variables
+  (
+    "DESIGNA a, b, c VT [X, XX, XXX]\na + b + c",
+    Program([], [
+      DesignaDestructure([ID("a"), ID("b"), ID("c")], DataArray([Numeral("X"), Numeral("XX"), Numeral("XXX")])),
+      ExpressionStatement(BinOp(BinOp(ID("a"), ID("b"), "SYMBOL_PLUS"), ID("c"), "SYMBOL_PLUS")),
+    ]),
+    ValInt(60),
+  ),
+  # destructure into individual use
+  (
+    "DEFINI pair (a, b) VT { REDI (a, b) }\nDESIGNA x, y VT INVOCA pair (V, II)\nDIC(x)\nDIC(y)",
+    Program([], [
+      Defini(ID("pair"), [ID("a"), ID("b")], [Redi([ID("a"), ID("b")])]),
+      DesignaDestructure([ID("x"), ID("y")], Invoca(ID("pair"), [Numeral("V"), Numeral("II")])),
+      ExpressionStatement(BuiltIn("DIC", [ID("x")])),
+      ExpressionStatement(BuiltIn("DIC", [ID("y")])),
+    ]),
+    ValStr("II"),
+    "V\nII\n",
+  ),
+]
+
+class TestDestructuring(unittest.TestCase):
+  @parameterized.expand(destructuring_tests)
+  def test_destructuring(self, source, nodes, value, output=""):
+    run_test(self, source, nodes, value, output)
+
+# --- Functions ---
+
+function_tests = [
+  (
+    "DEFINI bis (n) VT { REDI (n * II) }\nINVOCA bis (III)",
+    Program([], [
+      Defini(ID("bis"), [ID("n")], [Redi([BinOp(ID("n"), Numeral("II"), "SYMBOL_TIMES")])]),
+      ExpressionStatement(Invoca(ID("bis"), [Numeral("III")])),
+    ]),
+    ValInt(6),
+  ),
+  (
+    "DEFINI add (a, b) VT { REDI (a + b) }\nINVOCA add (III, IV)",
+    Program([], [
+      Defini(ID("add"), [ID("a"), ID("b")], [Redi([BinOp(ID("a"), ID("b"), "SYMBOL_PLUS")])]),
+      ExpressionStatement(Invoca(ID("add"), [Numeral("III"), Numeral("IV")])),
+    ]),
+    ValInt(7),
+  ),
+  # Fibonacci: fib(n<3)=1, fib(n)=fib(n-1)+fib(n-2)
+  (
+    "DEFINI fib (n) VT {\nSI n MINVS III TVNC { REDI (I) } ALIVD { REDI (INVOCA fib (n - I) + INVOCA fib (n - II)) }\n}\nINVOCA fib (VII)",
+    Program([], [
+      Defini(ID("fib"), [ID("n")], [
+        SiStatement(
+          BinOp(ID("n"), Numeral("III"), "KEYWORD_MINVS"),
+          [Redi([Numeral("I")])],
+          [Redi([BinOp(
+            Invoca(ID("fib"), [BinOp(ID("n"), Numeral("I"), "SYMBOL_MINUS")]),
+            Invoca(ID("fib"), [BinOp(ID("n"), Numeral("II"), "SYMBOL_MINUS")]),
+            "SYMBOL_PLUS",
+          )])],
+        ),
+      ]),
+      ExpressionStatement(Invoca(ID("fib"), [Numeral("VII")])),
+    ]),
+    ValInt(13),
+  ),
+]
+
+class TestFunctions(unittest.TestCase):
+  @parameterized.expand(function_tests)
+  def test_functions(self, source, nodes, value):
+    run_test(self, source, nodes, value)
+
+# --- Function edge cases ---
+
+function_edge_tests = [
+  # no explicit REDI → returns ValNul
+  ("DEFINI f () VT { I }\nINVOCA f ()",
+    Program([], [Defini(ID("f"), [], [ExpressionStatement(Numeral("I"))]), ExpressionStatement(Invoca(ID("f"), []))]),
+    ValNul()),
+  # REDI multiple values → ValList
+  (
+    "DEFINI pair (a, b) VT { REDI (a, b) }\nINVOCA pair (I, II)",
+    Program([], [
+      Defini(ID("pair"), [ID("a"), ID("b")], [Redi([ID("a"), ID("b")])]),
+      ExpressionStatement(Invoca(ID("pair"), [Numeral("I"), Numeral("II")])),
+    ]),
+    ValList([ValInt(1), ValInt(2)]),
+  ),
+  # function doesn't mutate outer vtable
+  (
+    "DESIGNA x VT I\nDEFINI f () VT { DESIGNA x VT V\nREDI (x) }\nINVOCA f ()\nx",
+    Program([], [
+      Designa(ID("x"), Numeral("I")),
+      Defini(ID("f"), [], [Designa(ID("x"), Numeral("V")), Redi([ID("x")])]),
+      ExpressionStatement(Invoca(ID("f"), [])),
+      ExpressionStatement(ID("x")),
+    ]),
+    ValInt(1),
+  ),
+  # function can read outer vtable (closure-like)
+  (
+    "DESIGNA x VT VII\nDEFINI f () VT { REDI (x) }\nINVOCA f ()",
+    Program([], [
+      Designa(ID("x"), Numeral("VII")),
+      Defini(ID("f"), [], [Redi([ID("x")])]),
+      ExpressionStatement(Invoca(ID("f"), [])),
+    ]),
+    ValInt(7),
+  ),
+  # parameter shadows outer variable inside function
+  (
+    "DESIGNA n VT I\nDEFINI f (n) VT { REDI (n * II) }\nINVOCA f (X)\nn",
+    Program([], [
+      Designa(ID("n"), Numeral("I")),
+      Defini(ID("f"), [ID("n")], [Redi([BinOp(ID("n"), Numeral("II"), "SYMBOL_TIMES")])]),
+      ExpressionStatement(Invoca(ID("f"), [Numeral("X")])),
+      ExpressionStatement(ID("n")),
+    ]),
+    ValInt(1),
+  ),
+  # function aliasing: assign f to g, invoke via g
+  (
+    "DEFINI f (n) VT { REDI (n * II) }\nDESIGNA g VT f\nINVOCA g (V)",
+    Program([], [
+      Defini(ID("f"), [ID("n")], [Redi([BinOp(ID("n"), Numeral("II"), "SYMBOL_TIMES")])]),
+      Designa(ID("g"), ID("f")),
+      ExpressionStatement(Invoca(ID("g"), [Numeral("V")])),
+    ]),
+    ValInt(10),
+  ),
+  # alias is independent: redefining f doesn't affect g
+  (
+    "DEFINI f (n) VT { REDI (n * II) }\nDESIGNA g VT f\nDEFINI f (n) VT { REDI (n * III) }\nINVOCA g (V)",
+    Program([], [
+      Defini(ID("f"), [ID("n")], [Redi([BinOp(ID("n"), Numeral("II"), "SYMBOL_TIMES")])]),
+      Designa(ID("g"), ID("f")),
+      Defini(ID("f"), [ID("n")], [Redi([BinOp(ID("n"), Numeral("III"), "SYMBOL_TIMES")])]),
+      ExpressionStatement(Invoca(ID("g"), [Numeral("V")])),
+    ]),
+    ValInt(10),
+  ),
+  # REDI inside SI exits function, skips remaining statements in block
+  (
+    "DEFINI f () VT {\nSI VERITAS TVNC {\nREDI (I)\nREDI (II)\n}\n}\nINVOCA f ()",
+    Program([],[
+      Defini(ID("f"), [], [SiStatement(Bool(True),[Redi([Numeral("I")]),Redi([Numeral("II")])],None)]),
+      ExpressionStatement(Invoca(ID("f"),[]))
+    ]),
+    ValInt(1),
+  ),
+  # REDI inside DVM exits loop and function
+  (
+    "DEFINI f () VT {\nDESIGNA x VT I\nDVM FALSITAS FAC {\nREDI (x)\n}\n}\nINVOCA f ()",
+    Program([],[
+      Defini(ID("f"), [], [
+        Designa(ID("x"), Numeral("I")),
+        DumStatement(Bool(False), [Redi([ID("x")])])
+      ]),
+      ExpressionStatement(Invoca(ID("f"),[]))
+    ]),
+    ValInt(1),
+  ),
+  # REDI inside PER exits loop and function
+  (
+    "DEFINI f () VT {\nPER x IN [I, II, III] FAC {\nSI x EST II TVNC {\nREDI (x)\n}\n}\n}\nINVOCA f ()",
+    Program([],[
+      Defini(ID("f"), [], [
+        PerStatement(DataArray([Numeral("I"), Numeral("II"), Numeral("III")]), ID("x"), [
+          SiStatement(BinOp(ID("x"), Numeral("II"), "KEYWORD_EST"), [
+            Redi([ID("x")])
+          ], None)
+        ])
+      ]),
+      ExpressionStatement(Invoca(ID("f"),[]))
+    ]),
+    ValInt(2),
+  ),
+  # REDI inside nested loops exits all loops and function
+  (
+    "DEFINI f () VT {\nDESIGNA x VT I\nDVM FALSITAS FAC {\nDVM FALSITAS FAC {\nREDI (x)\n}\n}\n}\nINVOCA f ()",
+    Program([],[
+      Defini(ID("f"), [], [
+        Designa(ID("x"), Numeral("I")),
+        DumStatement(Bool(False), [
+          DumStatement(Bool(False), [
+            Redi([ID("x")])
+          ])
+        ])
+      ]),
+      ExpressionStatement(Invoca(ID("f"),[]))
+    ]),
+    ValInt(1),
+  ),
+]
+
+class TestFunctionEdge(unittest.TestCase):
+  @parameterized.expand(function_edge_tests)
+  def test_function_edge(self, source, nodes, value):
+    run_test(self, source, nodes, value)

tests/02_test_con_flow.py

@@ -0,0 +1,418 @@
+from tests._helpers import (
+  unittest, parameterized, Fraction, time,
+  run_test, run_compiler_error_test,
+  ArrayIndex, ArraySlice, Bool, BinOp, BuiltIn, DataArray, DataDict, DataRangeArray,
+  Defini, Continva, Designa, DesignaDestructure, DesignaIndex, DumStatement,
+  Erumpe, ExpressionStatement, Fvnctio, ID, InterpolatedString, Invoca,
+  ModuleCall, Nullus, Numeral, PerStatement, Program, Redi, SiStatement,
+  String, TemptaStatement, UnaryMinus, UnaryNot, Fractio, frac_to_fraction,
+  fraction_to_frac, num_to_int, int_to_num, make_string,
+  ValInt, ValStr, ValBool, ValList, ValDict, ValNul, ValFunc, ValFrac,
+  CentvrionError, _RUNTIME_C, _cent_rng,
+  Lexer, Parser, compile_program,
+  os, subprocess, tempfile, StringIO, patch,
+)
+
+# --- Control flow ---
+
+control_tests = [
+  # SI without ALIVD — true branch
+  ("SI VERITAS TVNC { DESIGNA r VT I }\nr",
+    Program([], [SiStatement(Bool(True), [Designa(ID("r"), Numeral("I"))], None), ExpressionStatement(ID("r"))]),
+    ValInt(1)),
+  # SI without ALIVD — false branch
+  ("SI FALSITAS TVNC { DESIGNA r VT I }",
+    Program([], [SiStatement(Bool(False), [Designa(ID("r"), Numeral("I"))], None)]),
+    ValNul()),
+  # SI with ALIVD — true branch
+  ("SI VERITAS TVNC { DESIGNA r VT I } ALIVD { DESIGNA r VT II }\nr",
+    Program([], [SiStatement(Bool(True), [Designa(ID("r"), Numeral("I"))], [Designa(ID("r"), Numeral("II"))]), ExpressionStatement(ID("r"))]),
+    ValInt(1)),
+  # SI with ALIVD — false branch
+  ("SI FALSITAS TVNC { DESIGNA r VT I } ALIVD { DESIGNA r VT II }\nr",
+    Program([], [SiStatement(Bool(False), [Designa(ID("r"), Numeral("I"))], [Designa(ID("r"), Numeral("II"))]), ExpressionStatement(ID("r"))]),
+    ValInt(2)),
+  # SI with comparison — equal
+  ("SI I EST I TVNC { DESIGNA r VT I } ALIVD { DESIGNA r VT II }\nr",
+    Program([], [SiStatement(BinOp(Numeral("I"), Numeral("I"), "KEYWORD_EST"), [Designa(ID("r"), Numeral("I"))], [Designa(ID("r"), Numeral("II"))]), ExpressionStatement(ID("r"))]),
+    ValInt(1)),
+  # SI with comparison — unequal
+  ("SI I EST II TVNC { DESIGNA r VT I } ALIVD { DESIGNA r VT II }\nr",
+    Program([], [SiStatement(BinOp(Numeral("I"), Numeral("II"), "KEYWORD_EST"), [Designa(ID("r"), Numeral("I"))], [Designa(ID("r"), Numeral("II"))]), ExpressionStatement(ID("r"))]),
+    ValInt(2)),
+  # SI MINVS
+  ("SI I MINVS II TVNC { DESIGNA r VT I } ALIVD { DESIGNA r VT II }\nr",
+    Program([], [SiStatement(BinOp(Numeral("I"), Numeral("II"), "KEYWORD_MINVS"), [Designa(ID("r"), Numeral("I"))], [Designa(ID("r"), Numeral("II"))]), ExpressionStatement(ID("r"))]),
+    ValInt(1)),
+  # SI PLVS
+  ("SI II PLVS I TVNC { DESIGNA r VT I } ALIVD { DESIGNA r VT II }\nr",
+    Program([], [SiStatement(BinOp(Numeral("II"), Numeral("I"), "KEYWORD_PLVS"), [Designa(ID("r"), Numeral("I"))], [Designa(ID("r"), Numeral("II"))]), ExpressionStatement(ID("r"))]),
+    ValInt(1)),
+  # ALIVD SI chain
+  (
+    "SI I EST II TVNC { DESIGNA r VT I } ALIVD SI I EST I TVNC { DESIGNA r VT II } ALIVD { DESIGNA r VT III }\nr",
+    Program([], [
+      SiStatement(
+        BinOp(Numeral("I"), Numeral("II"), "KEYWORD_EST"),
+        [Designa(ID("r"), Numeral("I"))],
+        [SiStatement(
+          BinOp(Numeral("I"), Numeral("I"), "KEYWORD_EST"),
+          [Designa(ID("r"), Numeral("II"))],
+          [Designa(ID("r"), Numeral("III"))],
+        )],
+      ),
+      ExpressionStatement(ID("r")),
+    ]),
+    ValInt(2),
+  ),
+  # DVM (while not): loops until condition is true
+  (
+    "DESIGNA x VT I\nDVM x EST III FAC {\nDESIGNA x VT x + I\n}\nx",
+    Program([], [
+      Designa(ID("x"), Numeral("I")),
+      DumStatement(BinOp(ID("x"), Numeral("III"), "KEYWORD_EST"), [Designa(ID("x"), BinOp(ID("x"), Numeral("I"), "SYMBOL_PLUS"))]),
+      ExpressionStatement(ID("x")),
+    ]),
+    ValInt(3),
+  ),
+  # DVM with ERVMPE — loop body prints (testing DIC + ERVMPE together)
+  ("DESIGNA x VT I\nDVM FALSITAS FAC {\nDIC(x)\nERVMPE\n}",
+    Program([], [
+      Designa(ID("x"), Numeral("I")),
+      DumStatement(Bool(False), [ExpressionStatement(BuiltIn("DIC", [ID("x")])), Erumpe()]),
+    ]),
+    ValStr("I"), "I\n"),
+  # AETERNVM is sugar for DVM FALSITAS — must produce the same AST.
+  ("DESIGNA x VT I\nAETERNVM FAC {\nDIC(x)\nERVMPE\n}",
+    Program([], [
+      Designa(ID("x"), Numeral("I")),
+      DumStatement(Bool(False), [ExpressionStatement(BuiltIn("DIC", [ID("x")])), Erumpe()]),
+    ]),
+    ValStr("I"), "I\n"),
+  # AETERNVM with counter + ERVMPE on condition
+  ("DESIGNA x VT I\nAETERNVM FAC {\nSI x EST III TVNC { ERVMPE }\nDESIGNA x VT x + I\n}\nx",
+    Program([], [
+      Designa(ID("x"), Numeral("I")),
+      DumStatement(Bool(False), [
+        SiStatement(BinOp(ID("x"), Numeral("III"), "KEYWORD_EST"), [Erumpe()], None),
+        Designa(ID("x"), BinOp(ID("x"), Numeral("I"), "SYMBOL_PLUS")),
+      ]),
+      ExpressionStatement(ID("x")),
+    ]),
+    ValInt(3)),
+  # AETERNVM with CONTINVA — skip printing III; ERVMPE after V.
+  # Return value is ValNul because the iteration that triggers ERVMPE runs
+  # Designa first (resetting last_val); we test on output, which is the point.
+  ("DESIGNA x VT NVLLVS\nAETERNVM FAC {\nDESIGNA x VT x + I\nSI x PLVS V TVNC { ERVMPE }\nSI x EST III TVNC { CONTINVA }\nDIC(x)\n}",
+    Program([], [
+      Designa(ID("x"), Nullus()),
+      DumStatement(Bool(False), [
+        Designa(ID("x"), BinOp(ID("x"), Numeral("I"), "SYMBOL_PLUS")),
+        SiStatement(BinOp(ID("x"), Numeral("V"), "KEYWORD_PLVS"), [Erumpe()], None),
+        SiStatement(BinOp(ID("x"), Numeral("III"), "KEYWORD_EST"), [Continva()], None),
+        ExpressionStatement(BuiltIn("DIC", [ID("x")])),
+      ]),
+    ]),
+    ValNul(), "I\nII\nIV\nV\n"),
+  # REDI inside AETERNVM (inside DEFINI) — exits both loop and function
+  (
+    "DEFINI f () VT {\nDESIGNA x VT I\nAETERNVM FAC {\nREDI (x)\n}\n}\nINVOCA f ()",
+    Program([], [
+      Defini(ID("f"), [], [
+        Designa(ID("x"), Numeral("I")),
+        DumStatement(Bool(False), [Redi([ID("x")])]),
+      ]),
+      ExpressionStatement(Invoca(ID("f"), [])),
+    ]),
+    ValInt(1),
+  ),
+  # PER foreach
+  ("PER i IN [I, II, III] FAC { DIC(i) }",
+    Program([], [PerStatement(DataArray([Numeral("I"), Numeral("II"), Numeral("III")]), ID("i"), [ExpressionStatement(BuiltIn("DIC", [ID("i")]))])]),
+    ValStr("III"), "I\nII\nIII\n"),
+  # DONICVM range loop
+  ("DONICVM i VT I VSQVE V FAC { DIC(i) }",
+    Program([], [PerStatement(DataRangeArray(Numeral("I"), Numeral("V")), ID("i"), [ExpressionStatement(BuiltIn("DIC", [ID("i")]))])]),
+    ValStr("V"), "I\nII\nIII\nIV\nV\n"),
+  # PER destructuring
+  ("PER a, b IN [[I, II], [III, IV]] FAC { DIC(a + b) }",
+    Program([], [PerStatement(
+      DataArray([DataArray([Numeral("I"), Numeral("II")]), DataArray([Numeral("III"), Numeral("IV")])]),
+      [ID("a"), ID("b")],
+      [ExpressionStatement(BuiltIn("DIC", [BinOp(ID("a"), ID("b"), "SYMBOL_PLUS")]))])]),
+    ValStr("VII"), "III\nVII\n"),
+  # PER destructuring: three variables
+  ("PER a, b, c IN [[I, II, III]] FAC { DIC(a + b + c) }",
+    Program([], [PerStatement(
+      DataArray([DataArray([Numeral("I"), Numeral("II"), Numeral("III")])]),
+      [ID("a"), ID("b"), ID("c")],
+      [ExpressionStatement(BuiltIn("DIC", [BinOp(BinOp(ID("a"), ID("b"), "SYMBOL_PLUS"), ID("c"), "SYMBOL_PLUS")]))])]),
+    ValStr("VI"), "VI\n"),
+]
+
+class TestControl(unittest.TestCase):
+  @parameterized.expand(control_tests)
+  def test_control(self, source, nodes, value, output=""):
+    run_test(self, source, nodes, value, output)
+
+# --- Loop edge cases ---
+
+loop_edge_tests = [
+  # [III VSQVE III] = [3] — single iteration
+  ("DONICVM i VT III VSQVE III FAC { DIC(i) }",
+    Program([], [PerStatement(DataRangeArray(Numeral("III"), Numeral("III")), ID("i"), [ExpressionStatement(BuiltIn("DIC", [ID("i")]))])]),
+    ValStr("III"), "III\n"),
+  # empty array — body never runs
+  ("PER i IN [] FAC { DIC(i) }",
+    Program([], [PerStatement(DataArray([]), ID("i"), [ExpressionStatement(BuiltIn("DIC", [ID("i")]))])]),
+    ValNul(), ""),
+  # PER breaks on element 2 — last assigned i is 2
+  ("PER i IN [I, II, III] FAC { SI i EST II TVNC { ERVMPE } }\ni",
+    Program([], [
+      PerStatement(
+        DataArray([Numeral("I"), Numeral("II"), Numeral("III")]),
+        ID("i"),
+        [SiStatement(BinOp(ID("i"), Numeral("II"), "KEYWORD_EST"), [Erumpe()], None)],
+      ),
+      ExpressionStatement(ID("i")),
+    ]),
+    ValInt(2), ""),
+  # nested DVM: inner always breaks; outer runs until btr==3
+  ("DESIGNA btr VT I\nDVM btr EST III FAC {\nDVM FALSITAS FAC {\nERVMPE\n}\nDESIGNA btr VT btr + I\n}\nbtr",
+    Program([], [
+      Designa(ID("btr"), Numeral("I")),
+      DumStatement(
+        BinOp(ID("btr"), Numeral("III"), "KEYWORD_EST"),
+        [DumStatement(Bool(False), [Erumpe()]), Designa(ID("btr"), BinOp(ID("btr"), Numeral("I"), "SYMBOL_PLUS"))],
+      ),
+      ExpressionStatement(ID("btr")),
+    ]),
+    ValInt(3), ""),
+  # nested PER: inner always breaks on first element; outer completes both iterations
+  # cnt starts at 1, increments twice → 3
+  ("DESIGNA cnt VT I\nPER i IN [I, II] FAC {\nPER k IN [I, II] FAC {\nERVMPE\n}\nDESIGNA cnt VT cnt + I\n}\ncnt",
+    Program([], [
+      Designa(ID("cnt"), Numeral("I")),
+      PerStatement(
+        DataArray([Numeral("I"), Numeral("II")]),
+        ID("i"),
+        [PerStatement(DataArray([Numeral("I"), Numeral("II")]), ID("k"), [Erumpe()]),
+         Designa(ID("cnt"), BinOp(ID("cnt"), Numeral("I"), "SYMBOL_PLUS"))],
+      ),
+      ExpressionStatement(ID("cnt")),
+    ]),
+    ValInt(3), ""),
+  # PER with CONTINVA: skip odd numbers, sum evens
+  # [I,II,III,IV] → skip I and III; cnt increments on II and IV → cnt = III
+  ("DESIGNA cnt VT I\nPER i IN [I, II, III, IV] FAC {\nSI i EST I AVT i EST III TVNC { CONTINVA }\nDESIGNA cnt VT cnt + I\n}\ncnt",
+    Program([], [
+      Designa(ID("cnt"), Numeral("I")),
+      PerStatement(
+        DataArray([Numeral("I"), Numeral("II"), Numeral("III"), Numeral("IV")]),
+        ID("i"),
+        [SiStatement(BinOp(BinOp(ID("i"), Numeral("I"), "KEYWORD_EST"), BinOp(ID("i"), Numeral("III"), "KEYWORD_EST"), "KEYWORD_AVT"), [Continva()], None),
+         Designa(ID("cnt"), BinOp(ID("cnt"), Numeral("I"), "SYMBOL_PLUS"))],
+      ),
+      ExpressionStatement(ID("cnt")),
+    ]),
+    ValInt(3), ""),
+  # DVM with CONTINVA: skip body when x is II, increment regardless
+  # x goes 1→2→3; on x=2 we continue (no DIC); DIC fires for x=1 and x=3
+  ("DESIGNA x VT I\nDVM x EST IV FAC {\nSI x EST II TVNC { DESIGNA x VT x + I\nCONTINVA }\nDIC(x)\nDESIGNA x VT x + I\n}\nx",
+    Program([], [
+      Designa(ID("x"), Numeral("I")),
+      DumStatement(
+        BinOp(ID("x"), Numeral("IV"), "KEYWORD_EST"),
+        [SiStatement(BinOp(ID("x"), Numeral("II"), "KEYWORD_EST"),
+          [Designa(ID("x"), BinOp(ID("x"), Numeral("I"), "SYMBOL_PLUS")), Continva()], None),
+         ExpressionStatement(BuiltIn("DIC", [ID("x")])),
+         Designa(ID("x"), BinOp(ID("x"), Numeral("I"), "SYMBOL_PLUS"))],
+      ),
+      ExpressionStatement(ID("x")),
+    ]),
+    ValInt(4), "I\nIII\n"),
+  # nested PER: CONTINVA in inner only skips rest of inner body; outer still increments
+  ("DESIGNA cnt VT I\nPER i IN [I, II] FAC {\nPER k IN [I, II] FAC {\nCONTINVA\nDESIGNA cnt VT cnt + I\n}\nDESIGNA cnt VT cnt + I\n}\ncnt",
+    Program([], [
+      Designa(ID("cnt"), Numeral("I")),
+      PerStatement(
+        DataArray([Numeral("I"), Numeral("II")]),
+        ID("i"),
+        [PerStatement(DataArray([Numeral("I"), Numeral("II")]), ID("k"),
+          [Continva(), Designa(ID("cnt"), BinOp(ID("cnt"), Numeral("I"), "SYMBOL_PLUS"))]),
+         Designa(ID("cnt"), BinOp(ID("cnt"), Numeral("I"), "SYMBOL_PLUS"))],
+      ),
+      ExpressionStatement(ID("cnt")),
+    ]),
+    ValInt(3), ""),
+  # DONICVM with CONTINVA: skip value III, count remaining (I VSQVE IV = [1,2,3,4], skip 3 → 3 increments)
+  ("DESIGNA cnt VT I\nDONICVM i VT I VSQVE IV FAC {\nSI i EST III TVNC { CONTINVA }\nDESIGNA cnt VT cnt + I\n}\ncnt",
+    Program([], [
+      Designa(ID("cnt"), Numeral("I")),
+      PerStatement(
+        DataRangeArray(Numeral("I"), Numeral("IV")),
+        ID("i"),
+        [SiStatement(BinOp(ID("i"), Numeral("III"), "KEYWORD_EST"), [Continva()], None),
+         Designa(ID("cnt"), BinOp(ID("cnt"), Numeral("I"), "SYMBOL_PLUS"))],
+      ),
+      ExpressionStatement(ID("cnt")),
+    ]),
+    ValInt(4)),
+  # DVM condition true from start — body never runs
+  ("DESIGNA x VT I\nDVM VERITAS FAC {\nDESIGNA x VT x + I\n}\nx",
+    Program([], [
+      Designa(ID("x"), Numeral("I")),
+      DumStatement(Bool(True), [Designa(ID("x"), BinOp(ID("x"), Numeral("I"), "SYMBOL_PLUS"))]),
+      ExpressionStatement(ID("x")),
+    ]),
+    ValInt(1), ""),
+  # two iterations: [I VSQVE II] = [1, 2]
+  ("DONICVM i VT I VSQVE II FAC { DIC(i) }",
+    Program([], [PerStatement(DataRangeArray(Numeral("I"), Numeral("II")), ID("i"), [ExpressionStatement(BuiltIn("DIC", [ID("i")]))])]),
+    ValStr("II"), "I\nII\n"),
+  # single iteration: [I VSQVE I] = [1]
+  ("DONICVM i VT I VSQVE I FAC { DIC(i) }",
+    Program([], [PerStatement(DataRangeArray(Numeral("I"), Numeral("I")), ID("i"), [ExpressionStatement(BuiltIn("DIC", [ID("i")]))])]),
+    ValStr("I"), "I\n"),
+  # empty range: [V VSQVE I] = []
+  ("DESIGNA x VT NVLLVS\nDONICVM i VT V VSQVE I FAC { DESIGNA x VT x + i }\nx",
+    Program([], [Designa(ID("x"), Nullus()),
+                 PerStatement(DataRangeArray(Numeral("V"), Numeral("I")), ID("i"),
+                   [Designa(ID("x"), BinOp(ID("x"), ID("i"), "SYMBOL_PLUS"))]),
+                 ExpressionStatement(ID("x"))]),
+    ValNul(), ""),
+  # PER destructuring with ERVMPE
+  ("DESIGNA r VT I\nPER a, b IN [[I, II], [III, IV], [V, VI]] FAC {\nSI a EST III TVNC { ERVMPE }\nDESIGNA r VT r + a + b\n}\nr",
+    Program([], [
+      Designa(ID("r"), Numeral("I")),
+      PerStatement(
+        DataArray([DataArray([Numeral("I"), Numeral("II")]), DataArray([Numeral("III"), Numeral("IV")]), DataArray([Numeral("V"), Numeral("VI")])]),
+        [ID("a"), ID("b")],
+        [SiStatement(BinOp(ID("a"), Numeral("III"), "KEYWORD_EST"), [Erumpe()], None),
+         Designa(ID("r"), BinOp(BinOp(ID("r"), ID("a"), "SYMBOL_PLUS"), ID("b"), "SYMBOL_PLUS"))],
+      ),
+      ExpressionStatement(ID("r")),
+    ]),
+    ValInt(4)),  # 1 + 1 + 2 = 4, breaks before [III, IV]
+  # PER destructuring with REDI
+  ("DEFINI f () VT {\nPER a, b IN [[I, II], [III, IV]] FAC {\nSI a EST III TVNC { REDI (b) }\n}\n}\nINVOCA f ()",
+    Program([], [
+      Defini(ID("f"), [],
+        [PerStatement(
+          DataArray([DataArray([Numeral("I"), Numeral("II")]), DataArray([Numeral("III"), Numeral("IV")])]),
+          [ID("a"), ID("b")],
+          [SiStatement(BinOp(ID("a"), Numeral("III"), "KEYWORD_EST"), [Redi([ID("b")])], None)],
+        )]),
+      ExpressionStatement(Invoca(ID("f"), [])),
+    ]),
+    ValInt(4)),  # returns b=IV when a=III
+  # DONICVM GRADV II, endpoint hit exactly: [I, III, V]
+  ("DONICVM i VT I VSQVE V GRADV II FAC { DIC(i) }",
+    Program([], [PerStatement(
+      DataRangeArray(Numeral("I"), Numeral("V"), Numeral("II")),
+      ID("i"),
+      [ExpressionStatement(BuiltIn("DIC", [ID("i")]))])]),
+    ValStr("V"), "I\nIII\nV\n"),
+  # DONICVM GRADV II, endpoint overshot: VI excluded, stops at V
+  ("DONICVM i VT I VSQVE VI GRADV II FAC { DIC(i) }",
+    Program([], [PerStatement(
+      DataRangeArray(Numeral("I"), Numeral("VI"), Numeral("II")),
+      ID("i"),
+      [ExpressionStatement(BuiltIn("DIC", [ID("i")]))])]),
+    ValStr("V"), "I\nIII\nV\n"),
+  # DONICVM GRADV I is equivalent to default step
+  ("DONICVM i VT I VSQVE III GRADV I FAC { DIC(i) }",
+    Program([], [PerStatement(
+      DataRangeArray(Numeral("I"), Numeral("III"), Numeral("I")),
+      ID("i"),
+      [ExpressionStatement(BuiltIn("DIC", [ID("i")]))])]),
+    ValStr("III"), "I\nII\nIII\n"),
+  # DONICVM descending by I
+  ("CVM SVBNVLLA\nDONICVM i VT V VSQVE I GRADV - I FAC { DIC(i) }",
+    Program([ModuleCall("SVBNVLLA")], [PerStatement(
+      DataRangeArray(Numeral("V"), Numeral("I"), UnaryMinus(Numeral("I"))),
+      ID("i"),
+      [ExpressionStatement(BuiltIn("DIC", [ID("i")]))])]),
+    ValStr("I"), "V\nIV\nIII\nII\nI\n"),
+  # DONICVM descending by II, endpoint overshot
+  ("CVM SVBNVLLA\nDONICVM i VT X VSQVE I GRADV - II FAC { DIC(i) }",
+    Program([ModuleCall("SVBNVLLA")], [PerStatement(
+      DataRangeArray(Numeral("X"), Numeral("I"), UnaryMinus(Numeral("II"))),
+      ID("i"),
+      [ExpressionStatement(BuiltIn("DIC", [ID("i")]))])]),
+    ValStr("II"), "X\nVIII\nVI\nIV\nII\n"),
+  # DONICVM with step bound to a variable
+  ("DESIGNA s VT II\nDONICVM i VT I VSQVE V GRADV s FAC { DIC(i) }",
+    Program([], [
+      Designa(ID("s"), Numeral("II")),
+      PerStatement(
+        DataRangeArray(Numeral("I"), Numeral("V"), ID("s")),
+        ID("i"),
+        [ExpressionStatement(BuiltIn("DIC", [ID("i")]))])]),
+    ValStr("V"), "I\nIII\nV\n"),
+  # DONICVM from == to with nonzero step: single iteration
+  ("DONICVM i VT III VSQVE III GRADV II FAC { DIC(i) }",
+    Program([], [PerStatement(
+      DataRangeArray(Numeral("III"), Numeral("III"), Numeral("II")),
+      ID("i"),
+      [ExpressionStatement(BuiltIn("DIC", [ID("i")]))])]),
+    ValStr("III"), "III\n"),
+  # DONICVM direction mismatch — negative step with ascending bounds: body never runs
+  ("CVM SVBNVLLA\nDESIGNA x VT NVLLVS\nDONICVM i VT I VSQVE X GRADV - I FAC { DESIGNA x VT x + i }\nx",
+    Program([ModuleCall("SVBNVLLA")], [
+      Designa(ID("x"), Nullus()),
+      PerStatement(
+        DataRangeArray(Numeral("I"), Numeral("X"), UnaryMinus(Numeral("I"))),
+        ID("i"),
+        [Designa(ID("x"), BinOp(ID("x"), ID("i"), "SYMBOL_PLUS"))]),
+      ExpressionStatement(ID("x"))]),
+    ValNul(), ""),
+  # Range-array literal with GRADV used via PER
+  ("PER i IN [I VSQVE V GRADV II] FAC { DIC(i) }",
+    Program([], [PerStatement(
+      DataRangeArray(Numeral("I"), Numeral("V"), Numeral("II")),
+      ID("i"),
+      [ExpressionStatement(BuiltIn("DIC", [ID("i")]))])]),
+    ValStr("V"), "I\nIII\nV\n"),
+  # DONICVM GRADV II with CONTINVA: skip value V, print the others
+  ("DONICVM i VT I VSQVE IX GRADV II FAC {\nSI i EST V TVNC { CONTINVA }\nDIC(i)\n}",
+    Program([], [PerStatement(
+      DataRangeArray(Numeral("I"), Numeral("IX"), Numeral("II")),
+      ID("i"),
+      [SiStatement(BinOp(ID("i"), Numeral("V"), "KEYWORD_EST"), [Continva()], None),
+       ExpressionStatement(BuiltIn("DIC", [ID("i")]))])]),
+    ValStr("IX"), "I\nIII\nVII\nIX\n"),
+  # DONICVM GRADV II with ERVMPE: stop at V (last successful DIC was III)
+  ("DONICVM i VT I VSQVE IX GRADV II FAC {\nSI i EST V TVNC { ERVMPE }\nDIC(i)\n}",
+    Program([], [PerStatement(
+      DataRangeArray(Numeral("I"), Numeral("IX"), Numeral("II")),
+      ID("i"),
+      [SiStatement(BinOp(ID("i"), Numeral("V"), "KEYWORD_EST"), [Erumpe()], None),
+       ExpressionStatement(BuiltIn("DIC", [ID("i")]))])]),
+    ValStr("III"), "I\nIII\n"),
+]
+
+class TestLoopEdge(unittest.TestCase):
+  @parameterized.expand(loop_edge_tests)
+  def test_loop_edge(self, source, nodes, value, output=""):
+    run_test(self, source, nodes, value, output)
+
+# --- SI/DVM: boolean condition enforcement ---
+
+dvm_bool_condition_tests = [
+  # DVM exits when condition becomes true (boolean comparison)
+  (
+    "DESIGNA x VT I\nDVM x PLVS III FAC {\nDESIGNA x VT x + I\n}\nx",
+    Program([], [
+      Designa(ID("x"), Numeral("I")),
+      DumStatement(BinOp(ID("x"), Numeral("III"), "KEYWORD_PLVS"), [Designa(ID("x"), BinOp(ID("x"), Numeral("I"), "SYMBOL_PLUS"))]),
+      ExpressionStatement(ID("x")),
+    ]),
+    ValInt(4),
+  ),
+]
+
+class TestDvmBoolCondition(unittest.TestCase):
+  @parameterized.expand(dvm_bool_condition_tests)
+  def test_dvm_bool_condition(self, source, nodes, value):
+    run_test(self, source, nodes, value)

tests/03_test_builtins.py

@@ -0,0 +1,226 @@
+from tests._helpers import (
+  unittest, parameterized, Fraction, time,
+  run_test, run_compiler_error_test,
+  ArrayIndex, ArraySlice, Bool, BinOp, BuiltIn, DataArray, DataDict, DataRangeArray,
+  Defini, Continva, Designa, DesignaDestructure, DesignaIndex, DumStatement,
+  Erumpe, ExpressionStatement, Fvnctio, ID, InterpolatedString, Invoca,
+  ModuleCall, Nullus, Numeral, PerStatement, Program, Redi, SiStatement,
+  String, TemptaStatement, UnaryMinus, UnaryNot, Fractio, frac_to_fraction,
+  fraction_to_frac, num_to_int, int_to_num, make_string,
+  ValInt, ValStr, ValBool, ValList, ValDict, ValNul, ValFunc, ValFrac,
+  CentvrionError, _RUNTIME_C, _cent_rng,
+  Lexer, Parser, compile_program,
+  os, subprocess, tempfile, StringIO, patch,
+)
+
+# --- Builtins ---
+
+builtin_tests = [
+  ("AVDI_NVMERVS()", Program([], [ExpressionStatement(BuiltIn("AVDI_NVMERVS", []))]), ValInt(3), "", ["III"]),
+  ("AVDI_NVMERVS()", Program([], [ExpressionStatement(BuiltIn("AVDI_NVMERVS", []))]), ValInt(10), "", ["X"]),
+  ("CVM FORS\nDESIGNA a VT [I, II, III]\nDIC(a[FORTVITVS_NVMERVS(I, LONGITVDO(a))])", Program([ModuleCall("FORS")], [Designa(ID("a"), DataArray([Numeral("I"), Numeral("II"), Numeral("III")])), ExpressionStatement(BuiltIn("DIC", [ArrayIndex(ID("a"), BuiltIn("FORTVITVS_NVMERVS", [Numeral("I"), BuiltIn("LONGITVDO", [ID("a")])]))]))]), ValStr("I"), "I\n"),
+  ("AVDI()", Program([], [ExpressionStatement(BuiltIn("AVDI", []))]), ValStr("hello"), "", ["hello"]),
+  ("LONGITVDO([I, II, III])", Program([], [ExpressionStatement(BuiltIn("LONGITVDO", [DataArray([Numeral("I"), Numeral("II"), Numeral("III")])]))]), ValInt(3)),
+  ("LONGITVDO([])", Program([], [ExpressionStatement(BuiltIn("LONGITVDO", [DataArray([])]))]), ValInt(0)),
+  ('LONGITVDO("salve")', Program([], [ExpressionStatement(BuiltIn("LONGITVDO", [String("salve")]))]), ValInt(5)),
+  ('LONGITVDO("")', Program([], [ExpressionStatement(BuiltIn("LONGITVDO", [String("")]))]), ValInt(0)),
+  ("CVM FORS\nDIC(FORTVITA_ELECTIO([I, II, III]))", Program([ModuleCall("FORS")], [ExpressionStatement(BuiltIn("DIC", [BuiltIn("FORTVITA_ELECTIO", [DataArray([Numeral("I"), Numeral("II"), Numeral("III")])])]))]), ValStr("I"), "I\n"),
+  ("CVM FORS\nSEMEN(XLII)\nDIC(FORTVITVS_NVMERVS(I, C))", Program([ModuleCall("FORS")], [ExpressionStatement(BuiltIn("SEMEN", [Numeral("XLII")])), ExpressionStatement(BuiltIn("DIC", [BuiltIn("FORTVITVS_NVMERVS", [Numeral("I"), Numeral("C")])]))]), ValStr("XXXIII"), "XXXIII\n"),
+  # DECIMATIO: seed 42, 10 elements → removes 1 (element III)
+  ("CVM FORS\nSEMEN(XLII)\nDIC(DECIMATIO([I, II, III, IV, V, VI, VII, VIII, IX, X]))", Program([ModuleCall("FORS")], [ExpressionStatement(BuiltIn("SEMEN", [Numeral("XLII")])), ExpressionStatement(BuiltIn("DIC", [BuiltIn("DECIMATIO", [DataArray([Numeral("I"), Numeral("II"), Numeral("III"), Numeral("IV"), Numeral("V"), Numeral("VI"), Numeral("VII"), Numeral("VIII"), Numeral("IX"), Numeral("X")])])]))]), ValStr("[I II IV V VI VII VIII IX X]"), "[I II IV V VI VII VIII IX X]\n"),
+  # DECIMATIO: seed 1, 3 elements → 3//10=0, nothing removed
+  ("CVM FORS\nSEMEN(I)\nDIC(DECIMATIO([I, II, III]))", Program([ModuleCall("FORS")], [ExpressionStatement(BuiltIn("SEMEN", [Numeral("I")])), ExpressionStatement(BuiltIn("DIC", [BuiltIn("DECIMATIO", [DataArray([Numeral("I"), Numeral("II"), Numeral("III")])])]))]), ValStr("[I II III]"), "[I II III]\n"),
+  # DECIMATIO: empty array → empty array
+  ("CVM FORS\nDIC(DECIMATIO([]))", Program([ModuleCall("FORS")], [ExpressionStatement(BuiltIn("DIC", [BuiltIn("DECIMATIO", [DataArray([])])]))]), ValStr("[]"), "[]\n"),
+  # DECIMATIO: seed 42, 20 elements → removes 2 (elements XIII and XII)
+  ("CVM FORS\nSEMEN(XLII)\nDIC(DECIMATIO([I, II, III, IV, V, VI, VII, VIII, IX, X, XI, XII, XIII, XIV, XV, XVI, XVII, XVIII, XIX, XX]))", Program([ModuleCall("FORS")], [ExpressionStatement(BuiltIn("SEMEN", [Numeral("XLII")])), ExpressionStatement(BuiltIn("DIC", [BuiltIn("DECIMATIO", [DataArray([Numeral("I"), Numeral("II"), Numeral("III"), Numeral("IV"), Numeral("V"), Numeral("VI"), Numeral("VII"), Numeral("VIII"), Numeral("IX"), Numeral("X"), Numeral("XI"), Numeral("XII"), Numeral("XIII"), Numeral("XIV"), Numeral("XV"), Numeral("XVI"), Numeral("XVII"), Numeral("XVIII"), Numeral("XIX"), Numeral("XX")])])]))]), ValStr("[I II III IV V VI VII VIII IX X XI XIV XV XVI XVII XVIII XIX XX]"), "[I II III IV V VI VII VIII IX X XI XIV XV XVI XVII XVIII XIX XX]\n"),
+  # SENATVS: majority true → VERITAS
+  ("SENATVS(VERITAS, VERITAS, FALSITAS)", Program([], [ExpressionStatement(BuiltIn("SENATVS", [Bool(True), Bool(True), Bool(False)]))]), ValBool(True)),
+  # SENATVS: majority false → FALSITAS
+  ("SENATVS(FALSITAS, FALSITAS, VERITAS)", Program([], [ExpressionStatement(BuiltIn("SENATVS", [Bool(False), Bool(False), Bool(True)]))]), ValBool(False)),
+  # SENATVS: tie → FALSITAS
+  ("SENATVS(VERITAS, FALSITAS)", Program([], [ExpressionStatement(BuiltIn("SENATVS", [Bool(True), Bool(False)]))]), ValBool(False)),
+  # SENATVS: 4-arg tie → FALSITAS
+  ("SENATVS(VERITAS, VERITAS, FALSITAS, FALSITAS)", Program([], [ExpressionStatement(BuiltIn("SENATVS", [Bool(True), Bool(True), Bool(False), Bool(False)]))]), ValBool(False)),
+  # SENATVS: single true → VERITAS
+  ("SENATVS(VERITAS)", Program([], [ExpressionStatement(BuiltIn("SENATVS", [Bool(True)]))]), ValBool(True)),
+  # SENATVS: single false → FALSITAS
+  ("SENATVS(FALSITAS)", Program([], [ExpressionStatement(BuiltIn("SENATVS", [Bool(False)]))]), ValBool(False)),
+  # SENATVS: empty → FALSITAS (vacuous)
+  ("SENATVS()", Program([], [ExpressionStatement(BuiltIn("SENATVS", []))]), ValBool(False)),
+  # SENATVS: all true <20><> VERITAS
+  ("SENATVS(VERITAS, VERITAS, VERITAS, VERITAS, VERITAS)", Program([], [ExpressionStatement(BuiltIn("SENATVS", [Bool(True), Bool(True), Bool(True), Bool(True), Bool(True)]))]), ValBool(True)),
+  # SENATVS: array input, majority true → VERITAS
+  ("SENATVS([VERITAS, VERITAS, FALSITAS])", Program([], [ExpressionStatement(BuiltIn("SENATVS", [DataArray([Bool(True), Bool(True), Bool(False)])]))]), ValBool(True)),
+  # SENATVS: array input, majority false → FALSITAS
+  ("SENATVS([FALSITAS, FALSITAS, VERITAS])", Program([], [ExpressionStatement(BuiltIn("SENATVS", [DataArray([Bool(False), Bool(False), Bool(True)])]))]), ValBool(False)),
+  # SENATVS: array input, empty → FALSITAS
+  ("SENATVS([])", Program([], [ExpressionStatement(BuiltIn("SENATVS", [DataArray([])]))]), ValBool(False)),
+  # ORDINA: sort integers
+  ("ORDINA([III, I, II])", Program([], [ExpressionStatement(BuiltIn("ORDINA", [DataArray([Numeral("III"), Numeral("I"), Numeral("II")])]))]), ValList([ValInt(1), ValInt(2), ValInt(3)])),
+  # ORDINA: sort strings
+  ('ORDINA(["c", "a", "b"])', Program([], [ExpressionStatement(BuiltIn("ORDINA", [DataArray([String("c"), String("a"), String("b")])]))]), ValList([ValStr("a"), ValStr("b"), ValStr("c")])),
+  # ORDINA: empty list
+  ("ORDINA([])", Program([], [ExpressionStatement(BuiltIn("ORDINA", [DataArray([])]))]), ValList([])),
+  # ORDINA: single element
+  ("ORDINA([V])", Program([], [ExpressionStatement(BuiltIn("ORDINA", [DataArray([Numeral("V")])]))]), ValList([ValInt(5)])),
+  # ORDINA: already sorted
+  ("ORDINA([I, II, III])", Program([], [ExpressionStatement(BuiltIn("ORDINA", [DataArray([Numeral("I"), Numeral("II"), Numeral("III")])]))]), ValList([ValInt(1), ValInt(2), ValInt(3)])),
+  # ORDINA: duplicates
+  ("ORDINA([II, I, II])", Program([], [ExpressionStatement(BuiltIn("ORDINA", [DataArray([Numeral("II"), Numeral("I"), Numeral("II")])]))]), ValList([ValInt(1), ValInt(2), ValInt(2)])),
+  # ORDINA: negative numbers
+  ("CVM SVBNVLLA\nORDINA([-II, III, -I])", Program([ModuleCall("SVBNVLLA")], [ExpressionStatement(BuiltIn("ORDINA", [DataArray([UnaryMinus(Numeral("II")), Numeral("III"), UnaryMinus(Numeral("I"))])]))]), ValList([ValInt(-2), ValInt(-1), ValInt(3)])),
+  # ORDINA: fractions only
+  ("CVM FRACTIO\nORDINA([IIIS, S, IIS])", Program([ModuleCall("FRACTIO")], [ExpressionStatement(BuiltIn("ORDINA", [DataArray([Fractio("IIIS"), Fractio("S"), Fractio("IIS")])]))]), ValList([ValFrac(Fraction(1, 2)), ValFrac(Fraction(5, 2)), ValFrac(Fraction(7, 2))])),
+  # ORDINA: mixed integers and fractions
+  ("CVM FRACTIO\nORDINA([III, S, II])", Program([ModuleCall("FRACTIO")], [ExpressionStatement(BuiltIn("ORDINA", [DataArray([Numeral("III"), Fractio("S"), Numeral("II")])]))]), ValList([ValFrac(Fraction(1, 2)), ValInt(2), ValInt(3)])),
+  # ORDINA: array passed via variable
+  ("DESIGNA x VT [III, I, II]\nORDINA(x)", Program([], [Designa(ID("x"), DataArray([Numeral("III"), Numeral("I"), Numeral("II")])), ExpressionStatement(BuiltIn("ORDINA", [ID("x")]))]), ValList([ValInt(1), ValInt(2), ValInt(3)])),
+  # TYPVS: integer
+  ("TYPVS(V)", Program([], [ExpressionStatement(BuiltIn("TYPVS", [Numeral("V")]))]), ValStr("NVMERVS")),
+  # TYPVS: string
+  ('TYPVS("hello")', Program([], [ExpressionStatement(BuiltIn("TYPVS", [String("hello")]))]), ValStr("LITTERA")),
+  # TYPVS: boolean
+  ("TYPVS(VERITAS)", Program([], [ExpressionStatement(BuiltIn("TYPVS", [Bool(True)]))]), ValStr("VERAX")),
+  # TYPVS: list
+  ("TYPVS([I, II])", Program([], [ExpressionStatement(BuiltIn("TYPVS", [DataArray([Numeral("I"), Numeral("II")])]))]), ValStr("CATALOGVS")),
+  # TYPVS: empty list
+  ("TYPVS([])", Program([], [ExpressionStatement(BuiltIn("TYPVS", [DataArray([])]))]), ValStr("CATALOGVS")),
+  # TYPVS: fraction
+  ("CVM FRACTIO\nTYPVS(S)", Program([ModuleCall("FRACTIO")], [ExpressionStatement(BuiltIn("TYPVS", [Fractio("S")]))]), ValStr("FRACTIO")),
+  # TYPVS: dict
+  ("TYPVS(TABVLA {})", Program([], [ExpressionStatement(BuiltIn("TYPVS", [DataDict([])]))]), ValStr("TABVLA")),
+  # TYPVS: function
+  ("TYPVS(FVNCTIO () VT { REDI(I) })", Program([], [ExpressionStatement(BuiltIn("TYPVS", [Fvnctio([], [Redi([Numeral("I")])])]))]), ValStr("FVNCTIO")),
+  # TYPVS: null
+  ("TYPVS(NVLLVS)", Program([], [ExpressionStatement(BuiltIn("TYPVS", [Nullus()]))]), ValStr("NVLLVS")),
+  # LITTERA: integer → Roman numeral
+  ("LITTERA(V)", Program([], [ExpressionStatement(BuiltIn("LITTERA", [Numeral("V")]))]), ValStr("V")),
+  # LITTERA: larger integer
+  ("LITTERA(MCMLXXXIV)", Program([], [ExpressionStatement(BuiltIn("LITTERA", [Numeral("MCMLXXXIV")]))]), ValStr("MCMLXXXIV")),
+  # LITTERA: zero → NVLLVS
+  ("LITTERA(I - I)", Program([], [ExpressionStatement(BuiltIn("LITTERA", [BinOp(Numeral("I"), Numeral("I"), "SYMBOL_MINUS")]))]), ValStr("NVLLVS")),
+  # LITTERA: string passthrough
+  ('LITTERA("salve")', Program([], [ExpressionStatement(BuiltIn("LITTERA", [String("salve")]))]), ValStr("salve")),
+  # LITTERA: empty string
+  ('LITTERA("")', Program([], [ExpressionStatement(BuiltIn("LITTERA", [String("")]))]), ValStr("")),
+  # LITTERA: VERITAS
+  ("LITTERA(VERITAS)", Program([], [ExpressionStatement(BuiltIn("LITTERA", [Bool(True)]))]), ValStr("VERITAS")),
+  # LITTERA: FALSITAS
+  ("LITTERA(FALSITAS)", Program([], [ExpressionStatement(BuiltIn("LITTERA", [Bool(False)]))]), ValStr("FALSITAS")),
+  # LITTERA: NVLLVS
+  ("LITTERA(NVLLVS)", Program([], [ExpressionStatement(BuiltIn("LITTERA", [Nullus()]))]), ValStr("NVLLVS")),
+  # LITTERA: array of integers
+  ("LITTERA([I, II, III])", Program([], [ExpressionStatement(BuiltIn("LITTERA", [DataArray([Numeral("I"), Numeral("II"), Numeral("III")])]))]), ValStr("[I II III]")),
+  # LITTERA: empty array
+  ("LITTERA([])", Program([], [ExpressionStatement(BuiltIn("LITTERA", [DataArray([])]))]), ValStr("[]")),
+  # LITTERA: dict with string keys (make_string emits bare keys, not quoted — matches DIC's output)
+  ('LITTERA(TABVLA {"a" VT I})', Program([], [ExpressionStatement(BuiltIn("LITTERA", [DataDict([(String("a"), Numeral("I"))])]))]), ValStr('{a VT I}')),
+  # LITTERA: fraction (requires FRACTIO module)
+  ("CVM FRACTIO\nLITTERA(S)", Program([ModuleCall("FRACTIO")], [ExpressionStatement(BuiltIn("LITTERA", [Fractio("S")]))]), ValStr("S")),
+  # LITTERA: negative integer
+  ("CVM SVBNVLLA\nLITTERA(-III)", Program([ModuleCall("SVBNVLLA")], [ExpressionStatement(BuiltIn("LITTERA", [UnaryMinus(Numeral("III"))]))]), ValStr("-III")),
+  # LITTERA: round-trips through NVMERVS
+  ('NVMERVS(LITTERA(VII))', Program([], [ExpressionStatement(BuiltIn("NVMERVS", [BuiltIn("LITTERA", [Numeral("VII")])]))]), ValInt(7)),
+  # LITTERA: concatenated with a string via &
+  ('LITTERA(V) & " est quinque"', Program([], [ExpressionStatement(BinOp(BuiltIn("LITTERA", [Numeral("V")]), String(" est quinque"), "SYMBOL_AMPERSAND"))]), ValStr("V est quinque")),
+  # LITTERA: via variable
+  ("DESIGNA x VT IX\nLITTERA(x)", Program([], [Designa(ID("x"), Numeral("IX")), ExpressionStatement(BuiltIn("LITTERA", [ID("x")]))]), ValStr("IX")),
+  # QVAERE: basic literal match
+  ('QVAERE("ab", "abcabc")', Program([], [ExpressionStatement(BuiltIn("QVAERE", [String("ab"), String("abcabc")]))]), ValList([ValStr("ab"), ValStr("ab")])),
+  # QVAERE: no match → empty list
+  ('QVAERE("xyz", "abc")', Program([], [ExpressionStatement(BuiltIn("QVAERE", [String("xyz"), String("abc")]))]), ValList([])),
+  # QVAERE: regex character class
+  ('QVAERE("[a-z]+", "abc123def")', Program([], [ExpressionStatement(BuiltIn("QVAERE", [String("[a-z]+"), String("abc123def")]))]), ValList([ValStr("abc"), ValStr("def")])),
+  # QVAERE: empty text → empty list
+  ('QVAERE("a", "")', Program([], [ExpressionStatement(BuiltIn("QVAERE", [String("a"), String("")]))]), ValList([])),
+  # QVAERE: capture groups still return full match
+  ('QVAERE("(a)(b)", "ab")', Program([], [ExpressionStatement(BuiltIn("QVAERE", [String("(a)(b)"), String("ab")]))]), ValList([ValStr("ab")])),
+  # QVAERE: empty pattern matches between every character
+  ('QVAERE("", "ab")', Program([], [ExpressionStatement(BuiltIn("QVAERE", [String(""), String("ab")]))]), ValList([ValStr(""), ValStr(""), ValStr("")])),
+  # QVAERE: dot matches any character
+  ('QVAERE(".", "ab")', Program([], [ExpressionStatement(BuiltIn("QVAERE", [String("."), String("ab")]))]), ValList([ValStr("a"), ValStr("b")])),
+  # SVBSTITVE: basic literal replacement
+  ('SVBSTITVE("a", "b", "aaa")', Program([], [ExpressionStatement(BuiltIn("SVBSTITVE", [String("a"), String("b"), String("aaa")]))]), ValStr("bbb")),
+  # SVBSTITVE: regex character class
+  ('SVBSTITVE("[0-9]+", "N", "abc123def456")', Program([], [ExpressionStatement(BuiltIn("SVBSTITVE", [String("[0-9]+"), String("N"), String("abc123def456")]))]), ValStr("abcNdefN")),
+  # SVBSTITVE: no match → string unchanged
+  ('SVBSTITVE("x", "y", "abc")', Program([], [ExpressionStatement(BuiltIn("SVBSTITVE", [String("x"), String("y"), String("abc")]))]), ValStr("abc")),
+  # SVBSTITVE: empty replacement (deletion)
+  ('SVBSTITVE("a", "", "banana")', Program([], [ExpressionStatement(BuiltIn("SVBSTITVE", [String("a"), String(""), String("banana")]))]), ValStr("bnn")),
+  # SVBSTITVE: empty text → empty string
+  ('SVBSTITVE("a", "b", "")', Program([], [ExpressionStatement(BuiltIn("SVBSTITVE", [String("a"), String("b"), String("")]))]), ValStr("")),
+  # SVBSTITVE: dot matches any character
+  ('SVBSTITVE(".", "x", "ab")', Program([], [ExpressionStatement(BuiltIn("SVBSTITVE", [String("."), String("x"), String("ab")]))]), ValStr("xx")),
+  # SVBSTITVE: backreference swaps two groups (Roman numerals)
+  ('SVBSTITVE("(a)(b)", "\\II\\I", "ab")', Program([], [ExpressionStatement(BuiltIn("SVBSTITVE", [String("(a)(b)"), String("\\II\\I"), String("ab")]))]), ValStr("ba")),
+  # SVBSTITVE: backreference with unmatched group (ignored)
+  ('SVBSTITVE("(a)(b)?", "\\I\\II", "a")', Program([], [ExpressionStatement(BuiltIn("SVBSTITVE", [String("(a)(b)?"), String("\\I\\II"), String("a")]))]), ValStr("a")),
+  # SVBSTITVE: Roman numeral quantifier in pattern
+  ("SVBSTITVE('a{III}', 'x', 'aaa')", Program([], [ExpressionStatement(BuiltIn("SVBSTITVE", [String("a{III}"), String("x"), String("aaa")]))]), ValStr("x")),
+  # QVAERE: Roman numeral quantifier — exact repetition
+  ("QVAERE('a{III}', 'aaaa')", Program([], [ExpressionStatement(BuiltIn("QVAERE", [String("a{III}"), String("aaaa")]))]), ValList([ValStr("aaa")])),
+  # QVAERE: Roman numeral quantifier — range
+  ("QVAERE('a{II,III}', 'aaaaaa')", Program([], [ExpressionStatement(BuiltIn("QVAERE", [String("a{II,III}"), String("aaaaaa")]))]), ValList([ValStr("aaa"), ValStr("aaa")])),
+  # QVAERE: Roman numeral quantifier — at-least
+  ("QVAERE('a{II,}', 'a aa aaa')", Program([], [ExpressionStatement(BuiltIn("QVAERE", [String("a{II,}"), String("a aa aaa")]))]), ValList([ValStr("aa"), ValStr("aaa")])),
+  # QVAERE: pattern backreference — repeated character
+  ("QVAERE('(.)\\I', 'aabcdd')", Program([], [ExpressionStatement(BuiltIn("QVAERE", [String("(.)\\I"), String("aabcdd")]))]), ValList([ValStr("aa"), ValStr("dd")])),
+  # QVAERE: pattern backreference — repeated group
+  ("QVAERE('(..)\\I', 'ababcc')", Program([], [ExpressionStatement(BuiltIn("QVAERE", [String("(..)\\I"), String("ababcc")]))]), ValList([ValStr("abab")])),
+  # NVMERVS: basic conversion
+  ('NVMERVS("XIV")', Program([], [ExpressionStatement(BuiltIn("NVMERVS", [String("XIV")]))]), ValInt(14)),
+  # NVMERVS: simple single numeral
+  ('NVMERVS("I")', Program([], [ExpressionStatement(BuiltIn("NVMERVS", [String("I")]))]), ValInt(1)),
+  # NVMERVS: large numeral
+  ('NVMERVS("MMMCMXCIX")', Program([], [ExpressionStatement(BuiltIn("NVMERVS", [String("MMMCMXCIX")]))]), ValInt(3999)),
+  # NVMERVS: subtractive form
+  ('NVMERVS("IX")', Program([], [ExpressionStatement(BuiltIn("NVMERVS", [String("IX")]))]), ValInt(9)),
+  # SCINDE: basic split
+  ('SCINDE("a,b,c", ",")', Program([], [ExpressionStatement(BuiltIn("SCINDE", [String("a,b,c"), String(",")]))]), ValList([ValStr("a"), ValStr("b"), ValStr("c")])),
+  # SCINDE: no match (delimiter not found)
+  ('SCINDE("abc", ",")', Program([], [ExpressionStatement(BuiltIn("SCINDE", [String("abc"), String(",")]))]), ValList([ValStr("abc")])),
+  # SCINDE: empty string
+  ('SCINDE("", ",")', Program([], [ExpressionStatement(BuiltIn("SCINDE", [String(""), String(",")]))]), ValList([ValStr("")])),
+  # SCINDE: multi-char delimiter
+  ('SCINDE("a::b::c", "::")', Program([], [ExpressionStatement(BuiltIn("SCINDE", [String("a::b::c"), String("::")]))]), ValList([ValStr("a"), ValStr("b"), ValStr("c")])),
+  # SCINDE: delimiter at edges
+  ('SCINDE(",a,", ",")', Program([], [ExpressionStatement(BuiltIn("SCINDE", [String(",a,"), String(",")]))]), ValList([ValStr(""), ValStr("a"), ValStr("")])),
+  # SCINDE: empty delimiter (split into chars)
+  ('SCINDE("abc", "")', Program([], [ExpressionStatement(BuiltIn("SCINDE", [String("abc"), String("")]))]), ValList([ValStr("a"), ValStr("b"), ValStr("c")])),
+  # MAIVSCVLA: basic lowercase→uppercase
+  ('MAIVSCVLA("hello")', Program([], [ExpressionStatement(BuiltIn("MAIVSCVLA", [String("hello")]))]), ValStr("HELLO")),
+  # MAIVSCVLA: mixed case
+  ('MAIVSCVLA("HeLLo")', Program([], [ExpressionStatement(BuiltIn("MAIVSCVLA", [String("HeLLo")]))]), ValStr("HELLO")),
+  # MAIVSCVLA: already uppercase (idempotence)
+  ('MAIVSCVLA("HELLO")', Program([], [ExpressionStatement(BuiltIn("MAIVSCVLA", [String("HELLO")]))]), ValStr("HELLO")),
+  # MAIVSCVLA: empty string
+  ('MAIVSCVLA("")', Program([], [ExpressionStatement(BuiltIn("MAIVSCVLA", [String("")]))]), ValStr("")),
+  # MAIVSCVLA: Roman-numeral-shaped ASCII (case-only, not numeral-aware)
+  ('MAIVSCVLA("xii")', Program([], [ExpressionStatement(BuiltIn("MAIVSCVLA", [String("xii")]))]), ValStr("XII")),
+  # MAIVSCVLA: non-alphabetic chars unchanged
+  ('MAIVSCVLA("a,b!1")', Program([], [ExpressionStatement(BuiltIn("MAIVSCVLA", [String("a,b!1")]))]), ValStr("A,B!1")),
+  # MAIVSCVLA: via variable
+  ('DESIGNA s VT "foo"\nDIC(MAIVSCVLA(s))', Program([], [Designa(ID("s"), String("foo")), ExpressionStatement(BuiltIn("DIC", [BuiltIn("MAIVSCVLA", [ID("s")])]))]), ValStr("FOO"), "FOO\n"),
+  # MAIVSCVLA: concatenated with &
+  ('MAIVSCVLA("hi") & "!"', Program([], [ExpressionStatement(BinOp(BuiltIn("MAIVSCVLA", [String("hi")]), String("!"), "SYMBOL_AMPERSAND"))]), ValStr("HI!")),
+  # MINVSCVLA: basic uppercase→lowercase
+  ('MINVSCVLA("HELLO")', Program([], [ExpressionStatement(BuiltIn("MINVSCVLA", [String("HELLO")]))]), ValStr("hello")),
+  # MINVSCVLA: mixed case
+  ('MINVSCVLA("HeLLo")', Program([], [ExpressionStatement(BuiltIn("MINVSCVLA", [String("HeLLo")]))]), ValStr("hello")),
+  # MINVSCVLA: already lowercase (idempotence)
+  ('MINVSCVLA("hello")', Program([], [ExpressionStatement(BuiltIn("MINVSCVLA", [String("hello")]))]), ValStr("hello")),
+  # MINVSCVLA: empty string
+  ('MINVSCVLA("")', Program([], [ExpressionStatement(BuiltIn("MINVSCVLA", [String("")]))]), ValStr("")),
+  # MINVSCVLA: Roman-numeral-shaped ASCII (case-only, not numeral-aware)
+  ('MINVSCVLA("XII")', Program([], [ExpressionStatement(BuiltIn("MINVSCVLA", [String("XII")]))]), ValStr("xii")),
+  # MINVSCVLA: non-alphabetic chars unchanged
+  ('MINVSCVLA("A,B!1")', Program([], [ExpressionStatement(BuiltIn("MINVSCVLA", [String("A,B!1")]))]), ValStr("a,b!1")),
+  # MINVSCVLA round-trips MAIVSCVLA on lowercase input
+  ('MINVSCVLA(MAIVSCVLA("hi"))', Program([], [ExpressionStatement(BuiltIn("MINVSCVLA", [BuiltIn("MAIVSCVLA", [String("hi")])]))]), ValStr("hi")),
+]
+
+class TestBuiltins(unittest.TestCase):
+  @parameterized.expand(builtin_tests)
+  def test_builtins(self, source, nodes, value, output="", input_lines=[]):
+    run_test(self, source, nodes, value, output, input_lines)

tests/04_test_numerals.py

@@ -0,0 +1,175 @@
+from tests._helpers import (
+  unittest, parameterized, Fraction, time,
+  run_test, run_compiler_error_test,
+  ArrayIndex, ArraySlice, Bool, BinOp, BuiltIn, DataArray, DataDict, DataRangeArray,
+  Defini, Continva, Designa, DesignaDestructure, DesignaIndex, DumStatement,
+  Erumpe, ExpressionStatement, Fvnctio, ID, InterpolatedString, Invoca,
+  ModuleCall, Nullus, Numeral, PerStatement, Program, Redi, SiStatement,
+  String, TemptaStatement, UnaryMinus, UnaryNot, Fractio, frac_to_fraction,
+  fraction_to_frac, num_to_int, int_to_num, make_string,
+  ValInt, ValStr, ValBool, ValList, ValDict, ValNul, ValFunc, ValFrac,
+  CentvrionError, _RUNTIME_C, _cent_rng,
+  Lexer, Parser, compile_program,
+  os, subprocess, tempfile, StringIO, patch,
+)
+
+
+# --- Roman numeral utilities ---
+
+class TestNumerals(unittest.TestCase):
+  # num_to_int: valid cases
+  def test_simple_numerals(self):
+    for s, n in [("I",1),("V",5),("X",10),("L",50),("C",100),("D",500),("M",1000)]:
+      self.assertEqual(num_to_int(s, False), n)
+
+  def test_subtractive_forms(self):
+    for s, n in [("IV",4),("IX",9),("XL",40),("XC",90),("CD",400),("CM",900)]:
+      self.assertEqual(num_to_int(s, False), n)
+
+  def test_complex_numerals(self):
+    for s, n in [("XLII",42),("XCIX",99),("MCMXCIX",1999),("MMMCMXCIX",3999)]:
+      self.assertEqual(num_to_int(s, False), n)
+
+  # num_to_int: invalid cases
+  def test_four_in_a_row_raises(self):
+    with self.assertRaises(Exception):
+      num_to_int("IIII", False)
+
+  def test_four_x_in_a_row_raises(self):
+    with self.assertRaises(Exception):
+      num_to_int("XXXX", False)
+
+  def test_invalid_subtractive_iix_raises(self):
+    # IIX is non-standard — I can't appear twice before X
+    with self.assertRaises(Exception):
+      num_to_int("IIX", False)
+
+  def test_invalid_subtractive_im_raises(self):
+    # I can only subtract from V and X, not M
+    with self.assertRaises(Exception):
+      num_to_int("IM", False)
+
+  def test_negative_without_svbnvlla_raises(self):
+    with self.assertRaises(CentvrionError):
+      num_to_int("-IV", False)
+
+  def test_negative_with_svbnvlla(self):
+    self.assertEqual(num_to_int("-IV", False, True), -4)
+    self.assertEqual(num_to_int("-XLII", False, True), -42)
+
+  # int_to_num: valid cases
+  def test_int_to_num(self):
+    for n, s in [(0,"NVLLVS"),(1,"I"),(4,"IV"),(9,"IX"),(40,"XL"),(42,"XLII"),(3999,"MMMCMXCIX")]:
+      self.assertEqual(int_to_num(n, False), s)
+
+  def test_int_to_num_above_3999_raises(self):
+    with self.assertRaises(Exception):
+      int_to_num(4000, False)
+
+  def test_int_to_num_magnvm(self):
+    # 4000 with MAGNVM enabled
+    self.assertEqual(int_to_num(4000, True), "MV_")
+
+  def test_num_to_int_magnvm_required(self):
+    # Numbers parsed from strings with _ require MAGNVM
+    with self.assertRaises(Exception):
+      num_to_int("V_", False)
+
+# --- Arithmetic: edge cases ---
+
+arithmetic_edge_tests = [
+  ("I - I", Program([], [ExpressionStatement(BinOp(Numeral("I"), Numeral("I"), "SYMBOL_MINUS"))]), ValInt(0)),          # result zero
+  ("I - V", Program([], [ExpressionStatement(BinOp(Numeral("I"), Numeral("V"), "SYMBOL_MINUS"))]), ValInt(-4)),         # negative result
+  ("I / V", Program([], [ExpressionStatement(BinOp(Numeral("I"), Numeral("V"), "SYMBOL_DIVIDE"))]), ValInt(0)),          # integer division → 0
+  ("M * M", Program([], [ExpressionStatement(BinOp(Numeral("M"), Numeral("M"), "SYMBOL_TIMES"))]), ValInt(1000000)),    # large intermediate (not displayed)
+  ("(I + II) * (IV - I)", Program([], [ExpressionStatement(BinOp(BinOp(Numeral("I"), Numeral("II"), "SYMBOL_PLUS"), BinOp(Numeral("IV"), Numeral("I"), "SYMBOL_MINUS"), "SYMBOL_TIMES"))]), ValInt(9)),  # nested parens
+  # NVLLVS coerces to 0 in integer arithmetic
+  ("NVLLVS + V", Program([], [ExpressionStatement(BinOp(Nullus(), Numeral("V"), "SYMBOL_PLUS"))]), ValInt(5)),
+  ("V + NVLLVS", Program([], [ExpressionStatement(BinOp(Numeral("V"), Nullus(), "SYMBOL_PLUS"))]), ValInt(5)),
+  ("NVLLVS + NVLLVS", Program([], [ExpressionStatement(BinOp(Nullus(), Nullus(), "SYMBOL_PLUS"))]), ValNul()),
+  ("NVLLVS - V", Program([], [ExpressionStatement(BinOp(Nullus(), Numeral("V"), "SYMBOL_MINUS"))]), ValInt(-5)),
+  ("V - NVLLVS", Program([], [ExpressionStatement(BinOp(Numeral("V"), Nullus(), "SYMBOL_MINUS"))]), ValInt(5)),
+  # NVLLVS coerces to 0 in modulo and division
+  ("NVLLVS RELIQVVM V", Program([], [ExpressionStatement(BinOp(Nullus(), Numeral("V"), "KEYWORD_RELIQVVM"))]), ValInt(0)),
+  ("NVLLVS / V", Program([], [ExpressionStatement(BinOp(Nullus(), Numeral("V"), "SYMBOL_DIVIDE"))]), ValInt(0)),
+  # floored division and modulo with negative operands (Python semantics)
+  ("CVM SVBNVLLA\n- VII RELIQVVM III", Program([ModuleCall("SVBNVLLA")], [ExpressionStatement(BinOp(UnaryMinus(Numeral("VII")), Numeral("III"), "KEYWORD_RELIQVVM"))]), ValInt(2)),
+  ("CVM SVBNVLLA\nVII RELIQVVM - III", Program([ModuleCall("SVBNVLLA")], [ExpressionStatement(BinOp(Numeral("VII"), UnaryMinus(Numeral("III")), "KEYWORD_RELIQVVM"))]), ValInt(-2)),
+  ("CVM SVBNVLLA\n- VII RELIQVVM - III", Program([ModuleCall("SVBNVLLA")], [ExpressionStatement(BinOp(UnaryMinus(Numeral("VII")), UnaryMinus(Numeral("III")), "KEYWORD_RELIQVVM"))]), ValInt(-1)),
+  ("CVM SVBNVLLA\n- VII / III", Program([ModuleCall("SVBNVLLA")], [ExpressionStatement(BinOp(UnaryMinus(Numeral("VII")), Numeral("III"), "SYMBOL_DIVIDE"))]), ValInt(-3)),
+  ("CVM SVBNVLLA\nVII / - III", Program([ModuleCall("SVBNVLLA")], [ExpressionStatement(BinOp(Numeral("VII"), UnaryMinus(Numeral("III")), "SYMBOL_DIVIDE"))]), ValInt(-3)),
+  ("CVM SVBNVLLA\n- VII / - III", Program([ModuleCall("SVBNVLLA")], [ExpressionStatement(BinOp(UnaryMinus(Numeral("VII")), UnaryMinus(Numeral("III")), "SYMBOL_DIVIDE"))]), ValInt(2)),
+  ("CVM SVBNVLLA\n- L RELIQVVM C", Program([ModuleCall("SVBNVLLA")], [ExpressionStatement(BinOp(UnaryMinus(Numeral("L")), Numeral("C"), "KEYWORD_RELIQVVM"))]), ValInt(50)),
+]
+
+class TestArithmeticEdge(unittest.TestCase):
+  @parameterized.expand(arithmetic_edge_tests)
+  def test_arithmetic_edge(self, source, nodes, value):
+    run_test(self, source, nodes, value)
+
+# --- MAGNVM module ---
+# (ValueError for 4000 without MAGNVM is already in error_tests)
+
+magnvm_tests = [
+  # M+M+M+M = 4000; MAGNVM allows display as "MV_"
+  ("CVM MAGNVM\nDIC(M + M + M + M)",
+    Program([ModuleCall("MAGNVM")], [ExpressionStatement(BuiltIn("DIC", [BinOp(BinOp(BinOp(Numeral("M"), Numeral("M"), "SYMBOL_PLUS"), Numeral("M"), "SYMBOL_PLUS"), Numeral("M"), "SYMBOL_PLUS")]))]),
+    ValStr("MV_"), "MV_\n"),
+  # I_ = 1000 with MAGNVM (same value as M, but written with thousands operator)
+  ("CVM MAGNVM\nI_",
+    Program([ModuleCall("MAGNVM")], [ExpressionStatement(Numeral("I_"))]),
+    ValInt(1000), ""),
+  # I_ + I_ = 2000; displayed as MM with MAGNVM
+  ("CVM MAGNVM\nDIC(I_ + I_)",
+    Program([ModuleCall("MAGNVM")], [ExpressionStatement(BuiltIn("DIC", [BinOp(Numeral("I_"), Numeral("I_"), "SYMBOL_PLUS")]))]),
+    ValStr("MM"), "MM\n"),
+]
+
+class TestMAGNVM(unittest.TestCase):
+  @parameterized.expand(magnvm_tests)
+  def test_magnvm(self, source, nodes, value, output=""):
+    run_test(self, source, nodes, value, output)
+
+# --- SVBNVLLA module (display of negatives) ---
+
+svbnvlla_display_tests = [
+  # DIC prints a negative numeral
+  ("CVM SVBNVLLA\nDIC(- III)",
+    Program([ModuleCall("SVBNVLLA")], [ExpressionStatement(BuiltIn("DIC", [UnaryMinus(Numeral("III"))]))]),
+    ValStr("-III"), "-III\n"),
+  # Concat operator & with a negative numeral
+  ('CVM SVBNVLLA\nDIC("x: " & - V)',
+    Program([ModuleCall("SVBNVLLA")], [ExpressionStatement(BuiltIn("DIC", [BinOp(String("x: "), UnaryMinus(Numeral("V")), "SYMBOL_AMPERSAND")]))]),
+    ValStr("x: -V"), "x: -V\n"),
+  # String interpolation of a negative numeral
+  ('CVM SVBNVLLA\nDIC("val: {- X}")',
+    Program([ModuleCall("SVBNVLLA")], [ExpressionStatement(BuiltIn("DIC", [InterpolatedString([String("val: "), UnaryMinus(Numeral("X"))])]))]),
+    ValStr("val: -X"), "val: -X\n"),
+  # DIC of LITTERA(negative numeral)
+  ("CVM SVBNVLLA\nDIC(LITTERA(- III))",
+    Program([ModuleCall("SVBNVLLA")], [ExpressionStatement(BuiltIn("DIC", [BuiltIn("LITTERA", [UnaryMinus(Numeral("III"))])]))]),
+    ValStr("-III"), "-III\n"),
+  # Combined with MAGNVM: negative of a number > 3999
+  ("CVM MAGNVM\nCVM SVBNVLLA\nDIC(- (M + M + M + M))",
+    Program([ModuleCall("MAGNVM"), ModuleCall("SVBNVLLA")], [ExpressionStatement(BuiltIn("DIC", [UnaryMinus(BinOp(BinOp(BinOp(Numeral("M"), Numeral("M"), "SYMBOL_PLUS"), Numeral("M"), "SYMBOL_PLUS"), Numeral("M"), "SYMBOL_PLUS"))]))]),
+    ValStr("-MV_"), "-MV_\n"),
+  # Negative fraction via int / -int
+  ("CVM FRACTIO\nCVM SVBNVLLA\nDIC(V / - II)",
+    Program([ModuleCall("FRACTIO"), ModuleCall("SVBNVLLA")], [ExpressionStatement(BuiltIn("DIC", [BinOp(Numeral("V"), UnaryMinus(Numeral("II")), "SYMBOL_DIVIDE")]))]),
+    ValStr("-IIS"), "-IIS\n"),
+  # Negative pure fraction (no integer part)
+  ("CVM FRACTIO\nCVM SVBNVLLA\nDIC(I / - II)",
+    Program([ModuleCall("FRACTIO"), ModuleCall("SVBNVLLA")], [ExpressionStatement(BuiltIn("DIC", [BinOp(Numeral("I"), UnaryMinus(Numeral("II")), "SYMBOL_DIVIDE")]))]),
+    ValStr("-S"), "-S\n"),
+  ("CVM FRACTIO\nCVM SVBNVLLA\nDIC(- S)",
+    Program([ModuleCall("FRACTIO"), ModuleCall("SVBNVLLA")], [ExpressionStatement(BuiltIn("DIC", [UnaryMinus(Fractio("S"))]))]),
+    ValStr("-S"), "-S\n"),
+  ("CVM FRACTIO\nCVM SVBNVLLA\nDIC(- IIS)",
+    Program([ModuleCall("FRACTIO"), ModuleCall("SVBNVLLA")], [ExpressionStatement(BuiltIn("DIC", [UnaryMinus(Fractio("IIS"))]))]),
+    ValStr("-IIS"), "-IIS\n"),
+]
+
+class TestSVBNVLLADisplay(unittest.TestCase):
+  @parameterized.expand(svbnvlla_display_tests)
+  def test_svbnvlla_display(self, source, nodes, value, output=""):
+    run_test(self, source, nodes, value, output)

tests/05_test_literals.py

@@ -0,0 +1,402 @@
+from tests._helpers import (
+  unittest, parameterized, Fraction, time,
+  run_test, run_compiler_error_test,
+  ArrayIndex, ArraySlice, Bool, BinOp, BuiltIn, DataArray, DataDict, DataRangeArray,
+  Defini, Continva, Designa, DesignaDestructure, DesignaIndex, DumStatement,
+  Erumpe, ExpressionStatement, Fvnctio, ID, InterpolatedString, Invoca,
+  ModuleCall, Nullus, Numeral, PerStatement, Program, Redi, SiStatement,
+  String, TemptaStatement, UnaryMinus, UnaryNot, Fractio, frac_to_fraction,
+  fraction_to_frac, num_to_int, int_to_num, make_string,
+  ValInt, ValStr, ValBool, ValList, ValDict, ValNul, ValFunc, ValFrac,
+  CentvrionError, _RUNTIME_C, _cent_rng,
+  Lexer, Parser, compile_program,
+  os, subprocess, tempfile, StringIO, patch,
+)
+
+
+# --- Repr ---
+
+repr_tests = [
+  ("string", String("hello"), "String(hello)"),
+  ("numeral", Numeral("III"), "Numeral(III)"),
+  ("bool_true", Bool(True), "Bool(True)"),
+  ("bool_false", Bool(False), "Bool(False)"),
+  ("nullus", Nullus(), "Nullus()"),
+  ("erumpe", Erumpe(), "Erumpe()"),
+  ("module_call", ModuleCall("FORS"), "FORS"),
+  ("id", ID("x"), "ID(x)"),
+  ("expression_stmt", ExpressionStatement(String("hi")), "ExpressionStatement(\n  String(hi)\n)"),
+  ("data_array", DataArray([Numeral("I"), Numeral("II")]), "Array([\n  Numeral(I),\n  Numeral(II)\n])"),
+  ("data_range_array", DataRangeArray(Numeral("I"), Numeral("X")), "RangeArray([\n  Numeral(I),\n  Numeral(X)\n])"),
+  ("designa", Designa(ID("x"), Numeral("III")), "Designa(\n  ID(x),\n  Numeral(III)\n)"),
+  ("binop", BinOp(Numeral("I"), Numeral("II"), "SYMBOL_PLUS"), "BinOp(\n  Numeral(I),\n  Numeral(II),\n  SYMBOL_PLUS\n)"),
+  ("redi", Redi([Numeral("I")]), "Redi([\n  Numeral(I)\n])"),
+  ("si_no_else", SiStatement(Bool(True), [ExpressionStatement(Erumpe())], None), "Si(\n  Bool(True),\n  statements([\n    ExpressionStatement(\n      Erumpe()\n    )\n  ]),\n  None\n)"),
+  ("si_with_else", SiStatement(Bool(True), [ExpressionStatement(Erumpe())], [ExpressionStatement(Erumpe())]), "Si(\n  Bool(True),\n  statements([\n    ExpressionStatement(\n      Erumpe()\n    )\n  ]),\n  statements([\n    ExpressionStatement(\n      Erumpe()\n    )\n  ])\n)"),
+  ("si_empty_else", SiStatement(Bool(True), [ExpressionStatement(Erumpe())], []), "Si(\n  Bool(True),\n  statements([\n    ExpressionStatement(\n      Erumpe()\n    )\n  ]),\n  statements([])\n)"),
+  ("dum", DumStatement(Bool(False), [ExpressionStatement(Erumpe())]), "Dum(\n  Bool(False),\n  statements([\n    ExpressionStatement(\n      Erumpe()\n    )\n  ])\n)"),
+  ("per", PerStatement(DataArray([Numeral("I")]), ID("i"), [ExpressionStatement(Erumpe())]), "Per(\n  Array([\n    Numeral(I)\n  ]),\n  ID(i),\n  statements([\n    ExpressionStatement(\n      Erumpe()\n    )\n  ])\n)"),
+  ("invoca", Invoca(ID("f"), [Numeral("I")]), "Invoca(\n  ID(f),\n  parameters([\n    Numeral(I)\n  ])\n)"),
+  ("builtin", BuiltIn("DIC", [String("hi")]), "Builtin(\n  DIC,\n  parameters([\n    String(hi)\n  ])\n)"),
+  ("defini", Defini(ID("f"), [ID("n")], [ExpressionStatement(Redi([Numeral("I")]))]), "Defini(\n  ID(f),\n  parameters([\n    ID(n)\n  ]),\n  statements([\n    ExpressionStatement(\n      Redi([\n        Numeral(I)\n      ])\n    )\n  ])\n)"),
+  ("program_no_modules", Program([], [ExpressionStatement(Numeral("I"))]), "modules([]),\nstatements([\n  ExpressionStatement(\n    Numeral(I)\n  )\n])"),
+  ("program_with_module", Program([ModuleCall("FORS")], [ExpressionStatement(Numeral("I"))]), "modules([\n  FORS\n]),\nstatements([\n  ExpressionStatement(\n    Numeral(I)\n  )\n])"),
+]
+
+class TestRepr(unittest.TestCase):
+  @parameterized.expand(repr_tests)
+  def test_repr(self, _, node, expected):
+    self.assertEqual(repr(node), expected)
+
+# --- make_string ---
+
+class TestMakeString(unittest.TestCase):
+  def test_str(self):
+    self.assertEqual(make_string(ValStr("hello")), "hello")
+
+  def test_int(self):
+    self.assertEqual(make_string(ValInt(3)), "III")
+
+  def test_int_zero(self):
+    self.assertEqual(make_string(ValInt(0)), "NVLLVS")
+
+  def test_bool_true(self):
+    self.assertEqual(make_string(ValBool(True)), "VERITAS")
+
+  def test_bool_false(self):
+    self.assertEqual(make_string(ValBool(False)), "FALSITAS")
+
+  def test_nul(self):
+    self.assertEqual(make_string(ValNul()), "NVLLVS")
+
+  def test_list(self):
+    self.assertEqual(make_string(ValList([ValInt(1), ValInt(2)])), "[I II]")
+
+  def test_empty_list(self):
+    self.assertEqual(make_string(ValList([])), "[]")
+
+  def test_nested_list(self):
+    self.assertEqual(
+      make_string(ValList([ValStr("a"), ValBool(True)])),
+      "[a VERITAS]"
+    )
+
+# --- DIC with non-integer types ---
+
+dic_type_tests = [
+  ("DIC(VERITAS)", Program([], [ExpressionStatement(BuiltIn("DIC", [Bool(True)]))]), ValStr("VERITAS"), "VERITAS\n"),
+  ("DIC(FALSITAS)", Program([], [ExpressionStatement(BuiltIn("DIC", [Bool(False)]))]), ValStr("FALSITAS"), "FALSITAS\n"),
+  ("DIC(NVLLVS)", Program([], [ExpressionStatement(BuiltIn("DIC", [Nullus()]))]), ValStr("NVLLVS"), "NVLLVS\n"),
+  ('DIC([I, II])', Program([], [ExpressionStatement(BuiltIn("DIC", [DataArray([Numeral("I"), Numeral("II")])]))]), ValStr("[I II]"), "[I II]\n"),
+  ('DIC("")', Program([], [ExpressionStatement(BuiltIn("DIC", [String("")]))]), ValStr(""), "\n"),
+  # arithmetic result printed as numeral
+  ("DIC(II + III)", Program([], [ExpressionStatement(BuiltIn("DIC", [BinOp(Numeral("II"), Numeral("III"), "SYMBOL_PLUS")]))]), ValStr("V"), "V\n"),
+  # integer 0 prints as NVLLVS
+  ("DIC(I - I)", Program([], [ExpressionStatement(BuiltIn("DIC", [BinOp(Numeral("I"), Numeral("I"), "SYMBOL_MINUS")]))]), ValStr("NVLLVS"), "NVLLVS\n"),
+  # multiple args of mixed types
+  ('DIC("x", VERITAS)', Program([], [ExpressionStatement(BuiltIn("DIC", [String("x"), Bool(True)]))]), ValStr("x VERITAS"), "x VERITAS\n"),
+]
+
+class TestDicTypes(unittest.TestCase):
+  @parameterized.expand(dic_type_tests)
+  def test_dic_types(self, source, nodes, value, output):
+    run_test(self, source, nodes, value, output)
+
+# --- String concatenation ---
+
+string_concat_tests = [
+  ('"hello" & " world"', Program([], [ExpressionStatement(BinOp(String("hello"), String(" world"), "SYMBOL_AMPERSAND"))]), ValStr("hello world")),
+  # NVLLVS coerces to "" in string context
+  ('NVLLVS & "hello"', Program([], [ExpressionStatement(BinOp(Nullus(), String("hello"), "SYMBOL_AMPERSAND"))]), ValStr("hello")),
+  ('"hello" & NVLLVS', Program([], [ExpressionStatement(BinOp(String("hello"), Nullus(), "SYMBOL_AMPERSAND"))]), ValStr("hello")),
+  ('NVLLVS & NVLLVS', Program([], [ExpressionStatement(BinOp(Nullus(), Nullus(), "SYMBOL_AMPERSAND"))]), ValStr("")),
+  # integers coerce to Roman numerals in string context
+  ('"value: " & V', Program([], [ExpressionStatement(BinOp(String("value: "), Numeral("V"), "SYMBOL_AMPERSAND"))]), ValStr("value: V")),
+  ('X & " items"', Program([], [ExpressionStatement(BinOp(Numeral("X"), String(" items"), "SYMBOL_AMPERSAND"))]), ValStr("X items")),
+]
+
+class TestStringConcat(unittest.TestCase):
+  @parameterized.expand(string_concat_tests)
+  def test_string_concat(self, source, nodes, value):
+    run_test(self, source, nodes, value)
+
+# --- String interpolation ---
+
+interpolation_tests = [
+  # basic variable interpolation
+  ('DESIGNA nomen VT "Marcus"\n"Salve, {nomen}!"',
+    Program([], [
+      Designa(ID("nomen"), String("Marcus")),
+      ExpressionStatement(InterpolatedString([String("Salve, "), ID("nomen"), String("!")]))
+    ]), ValStr("Salve, Marcus!")),
+  # arithmetic expression inside interpolation
+  ('DESIGNA x VT III\n"Sum: {x + II}"',
+    Program([], [
+      Designa(ID("x"), Numeral("III")),
+      ExpressionStatement(InterpolatedString([String("Sum: "), BinOp(ID("x"), Numeral("II"), "SYMBOL_PLUS")]))
+    ]), ValStr("Sum: V")),
+  # multiple interpolations
+  ('DESIGNA a VT I\nDESIGNA b VT II\n"{a} + {b} = {a + b}"',
+    Program([], [
+      Designa(ID("a"), Numeral("I")),
+      Designa(ID("b"), Numeral("II")),
+      ExpressionStatement(InterpolatedString([
+        ID("a"), String(" + "), ID("b"), String(" = "),
+        BinOp(ID("a"), ID("b"), "SYMBOL_PLUS"),
+      ]))
+    ]), ValStr("I + II = III")),
+  # escaped braces become literal
+  ('"use {{braces}}"',
+    Program([], [ExpressionStatement(String("use {braces}"))]),
+    ValStr("use {braces}")),
+  # single-quoted strings ignore braces
+  ("'hello {world}'",
+    Program([], [ExpressionStatement(String("hello {world}"))]),
+    ValStr("hello {world}")),
+  # integer coercion
+  ('DESIGNA n VT V\n"n is {n}"',
+    Program([], [
+      Designa(ID("n"), Numeral("V")),
+      ExpressionStatement(InterpolatedString([String("n is "), ID("n")]))
+    ]), ValStr("n is V")),
+  # boolean coercion
+  ('DESIGNA b VT VERITAS\n"value: {b}"',
+    Program([], [
+      Designa(ID("b"), Bool(True)),
+      ExpressionStatement(InterpolatedString([String("value: "), ID("b")]))
+    ]), ValStr("value: VERITAS")),
+  # NVLLVS coercion
+  ('"value: {NVLLVS}"',
+    Program([], [
+      ExpressionStatement(InterpolatedString([String("value: "), Nullus()]))
+    ]), ValStr("value: NVLLVS")),
+  # integer 0 interpolates as NVLLVS
+  ('"value: {I - I}"', Program([], [ExpressionStatement(InterpolatedString([String("value: "), BinOp(Numeral("I"), Numeral("I"), "SYMBOL_MINUS")]))]), ValStr("value: NVLLVS")),
+  # expression-only string (no literal parts around it)
+  ('DESIGNA x VT "hi"\n"{x}"',
+    Program([], [
+      Designa(ID("x"), String("hi")),
+      ExpressionStatement(InterpolatedString([ID("x")]))
+    ]), ValStr("hi")),
+  # adjacent interpolations
+  ('DESIGNA a VT "x"\nDESIGNA b VT "y"\n"{a}{b}"',
+    Program([], [
+      Designa(ID("a"), String("x")),
+      Designa(ID("b"), String("y")),
+      ExpressionStatement(InterpolatedString([ID("a"), ID("b")]))
+    ]), ValStr("xy")),
+  # function call inside interpolation
+  ("DEFINI f () VT {\nREDI (V)\n}\n\"result: {INVOCA f()}\"",
+    Program([], [
+      Defini(ID("f"), [], [Redi([Numeral("V")])]),
+      ExpressionStatement(InterpolatedString([String("result: "), Invoca(ID("f"), [])]))
+    ]), ValStr("result: V")),
+  # single-quoted string inside interpolation
+  ("DESIGNA x VT 'hello'\n\"{x & '!'}\"",
+    Program([], [
+      Designa(ID("x"), String("hello")),
+      ExpressionStatement(InterpolatedString([BinOp(ID("x"), String("!"), "SYMBOL_AMPERSAND")]))
+    ]), ValStr("hello!")),
+  # plain double-quoted string (no braces) still works
+  ('"hello world"',
+    Program([], [ExpressionStatement(String("hello world"))]),
+    ValStr("hello world")),
+  # interpolation in DIC output
+  ('DESIGNA name VT "Roma"\nDIC("Salve, {name}!")',
+    Program([], [
+      Designa(ID("name"), String("Roma")),
+      ExpressionStatement(BuiltIn("DIC", [InterpolatedString([String("Salve, "), ID("name"), String("!")])]))
+    ]), ValStr("Salve, Roma!"), "Salve, Roma!\n"),
+]
+
+class TestInterpolation(unittest.TestCase):
+  @parameterized.expand(interpolation_tests)
+  def test_interpolation(self, source, nodes, value, output=""):
+    run_test(self, source, nodes, value, output)
+
+# --- Escape sequences ---
+
+escape_tests = [
+  # \n → newline
+  ('"hello\\nworld"',
+    Program([], [ExpressionStatement(String("hello\nworld"))]),
+    ValStr("hello\nworld")),
+  # \t → tab
+  ('"col\\tcol"',
+    Program([], [ExpressionStatement(String("col\tcol"))]),
+    ValStr("col\tcol")),
+  # \r → carriage return
+  ('"line\\rover"',
+    Program([], [ExpressionStatement(String("line\rover"))]),
+    ValStr("line\rover")),
+  # \\ → literal backslash
+  ('"back\\\\slash"',
+    Program([], [ExpressionStatement(String("back\\slash"))]),
+    ValStr("back\\slash")),
+  # \" → literal double quote
+  ('"say \\"salve\\""',
+    Program([], [ExpressionStatement(String('say "salve"'))]),
+    ValStr('say "salve"')),
+  # \' → literal single quote in single-quoted string
+  ("'it\\'s'",
+    Program([], [ExpressionStatement(String("it's"))]),
+    ValStr("it's")),
+  # \n in single-quoted string
+  ("'hello\\nworld'",
+    Program([], [ExpressionStatement(String("hello\nworld"))]),
+    ValStr("hello\nworld")),
+  # escape inside interpolated string
+  ('DESIGNA name VT "Roma"\n"salve\\n{name}"',
+    Program([], [
+      Designa(ID("name"), String("Roma")),
+      ExpressionStatement(InterpolatedString([String("salve\n"), ID("name")]))
+    ]), ValStr("salve\nRoma")),
+  # DIC with newline escape
+  ('DIC("hello\\nworld")',
+    Program([], [ExpressionStatement(BuiltIn("DIC", [String("hello\nworld")]))]),
+    ValStr("hello\nworld"), "hello\nworld\n"),
+  # multiple escapes in one string
+  ('"\\t\\n\\\\"',
+    Program([], [ExpressionStatement(String("\t\n\\"))]),
+    ValStr("\t\n\\")),
+  # unknown escapes pass through (regex backrefs)
+  ('"\\1\\2"',
+    Program([], [ExpressionStatement(String("\\1\\2"))]),
+    ValStr("\\1\\2")),
+]
+
+class TestEscapeSequences(unittest.TestCase):
+  @parameterized.expand(escape_tests)
+  def test_escape(self, source, nodes, value, output=""):
+    run_test(self, source, nodes, value, output)
+
+# --- String index assignment ---
+
+string_index_assign_tests = [
+  # assign to middle character
+  ('DESIGNA s VT "ABCDE"\nDESIGNA s[III] VT "X"\ns',
+    Program([], [
+      Designa(ID("s"), String("ABCDE")),
+      DesignaIndex(ID("s"), [Numeral("III")], String("X")),
+      ExpressionStatement(ID("s")),
+    ]),
+    ValStr("ABXDE")),
+  # assign to first character
+  ('DESIGNA s VT "ABCDE"\nDESIGNA s[I] VT "Z"\ns',
+    Program([], [
+      Designa(ID("s"), String("ABCDE")),
+      DesignaIndex(ID("s"), [Numeral("I")], String("Z")),
+      ExpressionStatement(ID("s")),
+    ]),
+    ValStr("ZBCDE")),
+  # assign to last character
+  ('DESIGNA s VT "ABCDE"\nDESIGNA s[V] VT "Z"\ns',
+    Program([], [
+      Designa(ID("s"), String("ABCDE")),
+      DesignaIndex(ID("s"), [Numeral("V")], String("Z")),
+      ExpressionStatement(ID("s")),
+    ]),
+    ValStr("ABCDZ")),
+  # variable as index
+  ('DESIGNA s VT "ABCDE"\nDESIGNA i VT II\nDESIGNA s[i] VT "X"\ns',
+    Program([], [
+      Designa(ID("s"), String("ABCDE")),
+      Designa(ID("i"), Numeral("II")),
+      DesignaIndex(ID("s"), [ID("i")], String("X")),
+      ExpressionStatement(ID("s")),
+    ]),
+    ValStr("AXCDE")),
+  # string inside array
+  ('DESIGNA a VT ["ABC", "DEF"]\nDESIGNA a[I][II] VT "X"\na[I]',
+    Program([], [
+      Designa(ID("a"), DataArray([String("ABC"), String("DEF")])),
+      DesignaIndex(ID("a"), [Numeral("I"), Numeral("II")], String("X")),
+      ExpressionStatement(ArrayIndex(ID("a"), Numeral("I"))),
+    ]),
+    ValStr("AXC")),
+]
+
+class TestStringIndexAssign(unittest.TestCase):
+  @parameterized.expand(string_index_assign_tests)
+  def test_string_index_assign(self, source, nodes, value):
+    run_test(self, source, nodes, value)
+
+# --- String indexing ---
+
+string_index_tests = [
+  # first character
+  ('"SALVTE"[I]',
+    Program([], [ExpressionStatement(ArrayIndex(String("SALVTE"), Numeral("I")))]),
+    ValStr("S")),
+  # last character
+  ('"SALVTE"[VI]',
+    Program([], [ExpressionStatement(ArrayIndex(String("SALVTE"), Numeral("VI")))]),
+    ValStr("E")),
+  # middle character
+  ('"SALVTE"[III]',
+    Program([], [ExpressionStatement(ArrayIndex(String("SALVTE"), Numeral("III")))]),
+    ValStr("L")),
+  # string index via variable
+  ('DESIGNA s VT "SALVTE"\ns[II]',
+    Program([], [
+      Designa(ID("s"), String("SALVTE")),
+      ExpressionStatement(ArrayIndex(ID("s"), Numeral("II"))),
+    ]),
+    ValStr("A")),
+  # expression as index
+  ('"SALVTE"[I + II]',
+    Program([], [ExpressionStatement(ArrayIndex(
+      String("SALVTE"),
+      BinOp(Numeral("I"), Numeral("II"), "SYMBOL_PLUS")))]),
+    ValStr("L")),
+]
+
+class TestStringIndex(unittest.TestCase):
+  @parameterized.expand(string_index_tests)
+  def test_string_index(self, source, nodes, value):
+    run_test(self, source, nodes, value)
+
+# --- String slicing ---
+
+string_slice_tests = [
+  # substring from middle
+  ('"SALVTE"[II VSQVE IV]',
+    Program([], [ExpressionStatement(ArraySlice(
+      String("SALVTE"), Numeral("II"), Numeral("IV")))]),
+    ValStr("ALV")),
+  # full string slice
+  ('"SALVTE"[I VSQVE VI]',
+    Program([], [ExpressionStatement(ArraySlice(
+      String("SALVTE"), Numeral("I"), Numeral("VI")))]),
+    ValStr("SALVTE")),
+  # single-char slice
+  ('"SALVTE"[III VSQVE III]',
+    Program([], [ExpressionStatement(ArraySlice(
+      String("SALVTE"), Numeral("III"), Numeral("III")))]),
+    ValStr("L")),
+  # slice on variable
+  ('DESIGNA s VT "SALVTE"\ns[II VSQVE IV]',
+    Program([], [
+      Designa(ID("s"), String("SALVTE")),
+      ExpressionStatement(ArraySlice(ID("s"), Numeral("II"), Numeral("IV"))),
+    ]),
+    ValStr("ALV")),
+  # chaining: slice then index
+  ('"SALVTE"[I VSQVE III][II]',
+    Program([], [ExpressionStatement(ArrayIndex(
+      ArraySlice(String("SALVTE"), Numeral("I"), Numeral("III")),
+      Numeral("II")))]),
+    ValStr("A")),
+  # expression as slice bounds
+  ('"SALVTE"[I + I VSQVE II + II]',
+    Program([], [ExpressionStatement(ArraySlice(
+      String("SALVTE"),
+      BinOp(Numeral("I"), Numeral("I"), "SYMBOL_PLUS"),
+      BinOp(Numeral("II"), Numeral("II"), "SYMBOL_PLUS")))]),
+    ValStr("ALV")),
+]
+
+class TestStringSlice(unittest.TestCase):
+  @parameterized.expand(string_slice_tests)
+  def test_string_slice(self, source, nodes, value):
+    run_test(self, source, nodes, value)

tests/06_test_booleans.py

@@ -0,0 +1,223 @@
+from tests._helpers import (
+  unittest, parameterized, Fraction, time,
+  run_test, run_compiler_error_test,
+  ArrayIndex, ArraySlice, Bool, BinOp, BuiltIn, DataArray, DataDict, DataRangeArray,
+  Defini, Continva, Designa, DesignaDestructure, DesignaIndex, DumStatement,
+  Erumpe, ExpressionStatement, Fvnctio, ID, InterpolatedString, Invoca,
+  ModuleCall, Nullus, Numeral, PerStatement, Program, Redi, SiStatement,
+  String, TemptaStatement, UnaryMinus, UnaryNot, Fractio, frac_to_fraction,
+  fraction_to_frac, num_to_int, int_to_num, make_string,
+  ValInt, ValStr, ValBool, ValList, ValDict, ValNul, ValFunc, ValFrac,
+  CentvrionError, _RUNTIME_C, _cent_rng,
+  Lexer, Parser, compile_program,
+  os, subprocess, tempfile, StringIO, patch,
+)
+
+# --- Comparison operators ---
+
+comparison_tests = [
+  # EST on strings
+  ('\"hello\" EST \"hello\"', Program([], [ExpressionStatement(BinOp(String("hello"), String("hello"), "KEYWORD_EST"))]), ValBool(True)),
+  ('\"hello\" EST \"world\"', Program([], [ExpressionStatement(BinOp(String("hello"), String("world"), "KEYWORD_EST"))]), ValBool(False)),
+  # chain comparisons as conditions
+  ("SI III PLVS II TVNC { DESIGNA r VT I }\nr",
+    Program([], [SiStatement(BinOp(Numeral("III"), Numeral("II"), "KEYWORD_PLVS"), [Designa(ID("r"), Numeral("I"))], None), ExpressionStatement(ID("r"))]),
+    ValInt(1)),
+  ("SI II PLVS III TVNC { DESIGNA r VT I } ALIVD { DESIGNA r VT II }\nr",
+    Program([], [SiStatement(BinOp(Numeral("II"), Numeral("III"), "KEYWORD_PLVS"), [Designa(ID("r"), Numeral("I"))], [Designa(ID("r"), Numeral("II"))]), ExpressionStatement(ID("r"))]),
+    ValInt(2)),
+  # result of comparison is ValBool
+  ("I EST I", Program([], [ExpressionStatement(BinOp(Numeral("I"), Numeral("I"), "KEYWORD_EST"))]), ValBool(True)),
+  ("I EST II", Program([], [ExpressionStatement(BinOp(Numeral("I"), Numeral("II"), "KEYWORD_EST"))]), ValBool(False)),
+  ("I MINVS II", Program([], [ExpressionStatement(BinOp(Numeral("I"), Numeral("II"), "KEYWORD_MINVS"))]), ValBool(True)),
+  ("II MINVS I", Program([], [ExpressionStatement(BinOp(Numeral("II"), Numeral("I"), "KEYWORD_MINVS"))]), ValBool(False)),
+  ("II PLVS I", Program([], [ExpressionStatement(BinOp(Numeral("II"), Numeral("I"), "KEYWORD_PLVS"))]), ValBool(True)),
+  ("I PLVS II", Program([], [ExpressionStatement(BinOp(Numeral("I"), Numeral("II"), "KEYWORD_PLVS"))]), ValBool(False)),
+  # NVLLVS coerces to 0 in comparisons
+  ("V PLVS NVLLVS", Program([], [ExpressionStatement(BinOp(Numeral("V"), Nullus(), "KEYWORD_PLVS"))]), ValBool(True)),
+  ("NVLLVS MINVS V", Program([], [ExpressionStatement(BinOp(Nullus(), Numeral("V"), "KEYWORD_MINVS"))]), ValBool(True)),
+  # DISPAR (not-equal): mirrors EST semantics, negated
+  ("I DISPAR II", Program([], [ExpressionStatement(BinOp(Numeral("I"), Numeral("II"), "KEYWORD_DISPAR"))]), ValBool(True)),
+  ("I DISPAR I", Program([], [ExpressionStatement(BinOp(Numeral("I"), Numeral("I"), "KEYWORD_DISPAR"))]), ValBool(False)),
+  ('"hello" DISPAR "hello"', Program([], [ExpressionStatement(BinOp(String("hello"), String("hello"), "KEYWORD_DISPAR"))]), ValBool(False)),
+  ('"hello" DISPAR "world"', Program([], [ExpressionStatement(BinOp(String("hello"), String("world"), "KEYWORD_DISPAR"))]), ValBool(True)),
+  ("VERITAS DISPAR FALSITAS", Program([], [ExpressionStatement(BinOp(Bool(True), Bool(False), "KEYWORD_DISPAR"))]), ValBool(True)),
+  ("NVLLVS DISPAR NVLLVS", Program([], [ExpressionStatement(BinOp(Nullus(), Nullus(), "KEYWORD_DISPAR"))]), ValBool(False)),
+  # cross-type: an int and a string are never equal
+  ('I DISPAR "I"', Program([], [ExpressionStatement(BinOp(Numeral("I"), String("I"), "KEYWORD_DISPAR"))]), ValBool(True)),
+  # integer 0 equals NVLLVS
+  ("(I - I) EST NVLLVS", Program([], [ExpressionStatement(BinOp(BinOp(Numeral("I"), Numeral("I"), "SYMBOL_MINUS"), Nullus(), "KEYWORD_EST"))]), ValBool(True)),
+  ("NVLLVS EST (I - I)", Program([], [ExpressionStatement(BinOp(Nullus(), BinOp(Numeral("I"), Numeral("I"), "SYMBOL_MINUS"), "KEYWORD_EST"))]), ValBool(True)),
+  ("(I - I) DISPAR NVLLVS", Program([], [ExpressionStatement(BinOp(BinOp(Numeral("I"), Numeral("I"), "SYMBOL_MINUS"), Nullus(), "KEYWORD_DISPAR"))]), ValBool(False)),
+  ("NVLLVS DISPAR (I - I)", Program([], [ExpressionStatement(BinOp(Nullus(), BinOp(Numeral("I"), Numeral("I"), "SYMBOL_MINUS"), "KEYWORD_DISPAR"))]), ValBool(False)),
+  # non-zero integer does not equal NVLLVS
+  ("I EST NVLLVS", Program([], [ExpressionStatement(BinOp(Numeral("I"), Nullus(), "KEYWORD_EST"))]), ValBool(False)),
+  ("NVLLVS DISPAR I", Program([], [ExpressionStatement(BinOp(Nullus(), Numeral("I"), "KEYWORD_DISPAR"))]), ValBool(True)),
+  # EST / DISPAR on arrays
+  ("[I, II] EST [I, II]", Program([], [ExpressionStatement(BinOp(DataArray([Numeral("I"), Numeral("II")]), DataArray([Numeral("I"), Numeral("II")]), "KEYWORD_EST"))]), ValBool(True)),
+  ("[I, II] EST [I, III]", Program([], [ExpressionStatement(BinOp(DataArray([Numeral("I"), Numeral("II")]), DataArray([Numeral("I"), Numeral("III")]), "KEYWORD_EST"))]), ValBool(False)),
+  ("[I, II] EST [I, II, III]", Program([], [ExpressionStatement(BinOp(DataArray([Numeral("I"), Numeral("II")]), DataArray([Numeral("I"), Numeral("II"), Numeral("III")]), "KEYWORD_EST"))]), ValBool(False)),
+  ("[] EST []", Program([], [ExpressionStatement(BinOp(DataArray([]), DataArray([]), "KEYWORD_EST"))]), ValBool(True)),
+  ("[I, II] DISPAR [I, III]", Program([], [ExpressionStatement(BinOp(DataArray([Numeral("I"), Numeral("II")]), DataArray([Numeral("I"), Numeral("III")]), "KEYWORD_DISPAR"))]), ValBool(True)),
+  ("[I, II] DISPAR [I, II]", Program([], [ExpressionStatement(BinOp(DataArray([Numeral("I"), Numeral("II")]), DataArray([Numeral("I"), Numeral("II")]), "KEYWORD_DISPAR"))]), ValBool(False)),
+  # HAVD_PLVS (<=) and HAVD_MINVS (>=)
+  ("I HAVD_PLVS II",  Program([], [ExpressionStatement(BinOp(Numeral("I"),  Numeral("II"), "KEYWORD_HAVD_PLVS"))]),  ValBool(True)),
+  ("II HAVD_PLVS I",  Program([], [ExpressionStatement(BinOp(Numeral("II"), Numeral("I"),  "KEYWORD_HAVD_PLVS"))]),  ValBool(False)),
+  # equality boundary — the only case that distinguishes <= from <
+  ("II HAVD_PLVS II", Program([], [ExpressionStatement(BinOp(Numeral("II"), Numeral("II"), "KEYWORD_HAVD_PLVS"))]),  ValBool(True)),
+  ("II HAVD_MINVS I", Program([], [ExpressionStatement(BinOp(Numeral("II"), Numeral("I"),  "KEYWORD_HAVD_MINVS"))]), ValBool(True)),
+  ("I HAVD_MINVS II", Program([], [ExpressionStatement(BinOp(Numeral("I"),  Numeral("II"), "KEYWORD_HAVD_MINVS"))]), ValBool(False)),
+  # equality boundary — the only case that distinguishes >= from >
+  ("II HAVD_MINVS II",Program([], [ExpressionStatement(BinOp(Numeral("II"), Numeral("II"), "KEYWORD_HAVD_MINVS"))]), ValBool(True)),
+  # NVLLVS coerces to 0
+  ("V HAVD_MINVS NVLLVS", Program([], [ExpressionStatement(BinOp(Numeral("V"), Nullus(), "KEYWORD_HAVD_MINVS"))]), ValBool(True)),
+  ("NVLLVS HAVD_PLVS V",  Program([], [ExpressionStatement(BinOp(Nullus(), Numeral("V"), "KEYWORD_HAVD_PLVS"))]),  ValBool(True)),
+  ("NVLLVS HAVD_PLVS NVLLVS",  Program([], [ExpressionStatement(BinOp(Nullus(), Nullus(), "KEYWORD_HAVD_PLVS"))]),  ValBool(True)),
+  # precedence: * binds tighter, so II*III HAVD_PLVS VI parses as (II*III) HAVD_PLVS VI = 6 <= 6 = True
+  ("II * III HAVD_PLVS VI",
+    Program([], [ExpressionStatement(BinOp(BinOp(Numeral("II"), Numeral("III"), "SYMBOL_TIMES"), Numeral("VI"), "KEYWORD_HAVD_PLVS"))]),
+    ValBool(True)),
+  # control flow: SI ... HAVD_MINVS
+  ("SI II HAVD_MINVS II TVNC { DESIGNA r VT I } ALIVD { DESIGNA r VT II }\nr",
+    Program([], [SiStatement(BinOp(Numeral("II"), Numeral("II"), "KEYWORD_HAVD_MINVS"), [Designa(ID("r"), Numeral("I"))], [Designa(ID("r"), Numeral("II"))]), ExpressionStatement(ID("r"))]),
+    ValInt(1)),
+]
+
+class TestComparisons(unittest.TestCase):
+  @parameterized.expand(comparison_tests)
+  def test_comparisons(self, source, nodes, value):
+    run_test(self, source, nodes, value)
+
+# --- ET and AVT (boolean and/or) ---
+
+et_avt_tests = [
+  ("VERITAS ET VERITAS", Program([], [ExpressionStatement(BinOp(Bool(True), Bool(True), "KEYWORD_ET"))]), ValBool(True)),
+  ("VERITAS ET FALSITAS", Program([], [ExpressionStatement(BinOp(Bool(True), Bool(False), "KEYWORD_ET"))]), ValBool(False)),
+  ("FALSITAS ET VERITAS", Program([], [ExpressionStatement(BinOp(Bool(False), Bool(True), "KEYWORD_ET"))]), ValBool(False)),
+  ("FALSITAS ET FALSITAS", Program([], [ExpressionStatement(BinOp(Bool(False), Bool(False), "KEYWORD_ET"))]), ValBool(False)),
+  ("VERITAS AVT VERITAS", Program([], [ExpressionStatement(BinOp(Bool(True), Bool(True), "KEYWORD_AVT"))]), ValBool(True)),
+  ("VERITAS AVT FALSITAS", Program([], [ExpressionStatement(BinOp(Bool(True), Bool(False), "KEYWORD_AVT"))]), ValBool(True)),
+  ("FALSITAS AVT VERITAS", Program([], [ExpressionStatement(BinOp(Bool(False), Bool(True), "KEYWORD_AVT"))]), ValBool(True)),
+  ("FALSITAS AVT FALSITAS", Program([], [ExpressionStatement(BinOp(Bool(False), Bool(False), "KEYWORD_AVT"))]), ValBool(False)),
+  # short-circuit behavior: combined with comparisons
+  ("(I EST I) ET (II EST II)",
+    Program([], [ExpressionStatement(BinOp(BinOp(Numeral("I"), Numeral("I"), "KEYWORD_EST"), BinOp(Numeral("II"), Numeral("II"), "KEYWORD_EST"), "KEYWORD_ET"))]),
+    ValBool(True)),
+  ("(I EST II) AVT (II EST II)",
+    Program([], [ExpressionStatement(BinOp(BinOp(Numeral("I"), Numeral("II"), "KEYWORD_EST"), BinOp(Numeral("II"), Numeral("II"), "KEYWORD_EST"), "KEYWORD_AVT"))]),
+    ValBool(True)),
+  # used as SI condition
+  ("SI VERITAS ET VERITAS TVNC { DESIGNA r VT I } ALIVD { DESIGNA r VT II }\nr",
+    Program([], [SiStatement(BinOp(Bool(True), Bool(True), "KEYWORD_ET"), [Designa(ID("r"), Numeral("I"))], [Designa(ID("r"), Numeral("II"))]), ExpressionStatement(ID("r"))]),
+    ValInt(1)),
+  ("SI FALSITAS AVT FALSITAS TVNC { DESIGNA r VT I } ALIVD { DESIGNA r VT II }\nr",
+    Program([], [SiStatement(BinOp(Bool(False), Bool(False), "KEYWORD_AVT"), [Designa(ID("r"), Numeral("I"))], [Designa(ID("r"), Numeral("II"))]), ExpressionStatement(ID("r"))]),
+    ValInt(2)),
+  # short-circuit: right side not evaluated when result is determined
+  ("VERITAS AVT NVLLVS",
+    Program([], [ExpressionStatement(BinOp(Bool(True), Nullus(), "KEYWORD_AVT"))]),
+    ValBool(True)),
+  ("FALSITAS ET NVLLVS",
+    Program([], [ExpressionStatement(BinOp(Bool(False), Nullus(), "KEYWORD_ET"))]),
+    ValBool(False)),
+  # short-circuit with side-effect-prone expressions
+  ("DESIGNA x VT NVLLVS\nSI x EST NVLLVS AVT [I, II][x] EST I TVNC { DESIGNA r VT I } ALIVD { DESIGNA r VT II }\nr",
+    Program([], [
+      Designa(ID("x"), Nullus()),
+      SiStatement(
+        BinOp(BinOp(ID("x"), Nullus(), "KEYWORD_EST"), BinOp(ArrayIndex(DataArray([Numeral("I"), Numeral("II")]), ID("x")), Numeral("I"), "KEYWORD_EST"), "KEYWORD_AVT"),
+        [Designa(ID("r"), Numeral("I"))],
+        [Designa(ID("r"), Numeral("II"))]),
+      ExpressionStatement(ID("r"))]),
+    ValInt(1)),
+  ("DESIGNA x VT NVLLVS\nSI x DISPAR NVLLVS ET [I, II][x] EST I TVNC { DESIGNA r VT I } ALIVD { DESIGNA r VT II }\nr",
+    Program([], [
+      Designa(ID("x"), Nullus()),
+      SiStatement(
+        BinOp(BinOp(ID("x"), Nullus(), "KEYWORD_DISPAR"), BinOp(ArrayIndex(DataArray([Numeral("I"), Numeral("II")]), ID("x")), Numeral("I"), "KEYWORD_EST"), "KEYWORD_ET"),
+        [Designa(ID("r"), Numeral("I"))],
+        [Designa(ID("r"), Numeral("II"))]),
+      ExpressionStatement(ID("r"))]),
+    ValInt(2)),
+]
+
+class TestEtAvt(unittest.TestCase):
+  @parameterized.expand(et_avt_tests)
+  def test_et_avt(self, source, nodes, value):
+    run_test(self, source, nodes, value)
+
+# --- NON (boolean not) ---
+
+non_tests = [
+  ("NON VERITAS",
+    Program([], [ExpressionStatement(UnaryNot(Bool(True)))]),
+    ValBool(False)),
+  ("NON FALSITAS",
+    Program([], [ExpressionStatement(UnaryNot(Bool(False)))]),
+    ValBool(True)),
+  ("NON NON VERITAS",
+    Program([], [ExpressionStatement(UnaryNot(UnaryNot(Bool(True))))]),
+    ValBool(True)),
+  ("DESIGNA b VT I EST II\nNON b",
+    Program([], [Designa(ID("b"), BinOp(Numeral("I"), Numeral("II"), "KEYWORD_EST")), ExpressionStatement(UnaryNot(ID("b")))]),
+    ValBool(True)),
+  ("DESIGNA z VT I EST I\nNON z",
+    Program([], [Designa(ID("z"), BinOp(Numeral("I"), Numeral("I"), "KEYWORD_EST")), ExpressionStatement(UnaryNot(ID("z")))]),
+    ValBool(False)),
+  ("NON VERITAS AVT FALSITAS",
+    Program([], [ExpressionStatement(BinOp(UnaryNot(Bool(True)), Bool(False), "KEYWORD_AVT"))]),
+    ValBool(False)),
+  ("NON VERITAS EST FALSITAS",
+    Program([], [ExpressionStatement(BinOp(UnaryNot(Bool(True)), Bool(False), "KEYWORD_EST"))]),
+    ValBool(True)),
+]
+
+class TestNon(unittest.TestCase):
+  @parameterized.expand(non_tests)
+  def test_non(self, source, nodes, value):
+    run_test(self, source, nodes, value)
+
+# --- Values: equality and truthiness ---
+
+class TestValues(unittest.TestCase):
+  def test_valint_equality(self):
+    self.assertEqual(ValInt(3), ValInt(3))
+    self.assertNotEqual(ValInt(3), ValInt(4))
+
+  def test_valstr_equality(self):
+    self.assertEqual(ValStr("hi"), ValStr("hi"))
+    self.assertNotEqual(ValStr("hi"), ValStr("bye"))
+
+  def test_valbool_equality(self):
+    self.assertEqual(ValBool(True), ValBool(True))
+    self.assertNotEqual(ValBool(True), ValBool(False))
+
+  def test_valnul_equality(self):
+    self.assertEqual(ValNul(), ValNul())
+
+  def test_vallist_equality(self):
+    self.assertEqual(ValList([ValInt(1)]), ValList([ValInt(1)]))
+    self.assertNotEqual(ValList([ValInt(1)]), ValList([ValInt(2)]))
+    self.assertNotEqual(ValList([ValInt(1)]), ValList([]))
+
+  def test_valint_truthiness(self):
+    self.assertTrue(bool(ValInt(1)))
+    self.assertTrue(bool(ValInt(-1)))
+    self.assertFalse(bool(ValInt(0)))
+
+  def test_valstr_truthiness(self):
+    self.assertTrue(bool(ValStr("x")))
+    self.assertFalse(bool(ValStr("")))
+
+  def test_valbool_truthiness(self):
+    self.assertTrue(bool(ValBool(True)))
+    self.assertFalse(bool(ValBool(False)))
+
+  def test_vallist_truthiness(self):
+    self.assertTrue(bool(ValList([ValInt(1)])))
+    self.assertFalse(bool(ValList([])))
+
+  def test_cross_type_inequality(self):
+    self.assertNotEqual(ValInt(1), ValBool(True))
+    self.assertNotEqual(ValInt(0), ValNul())
+    self.assertNotEqual(ValStr(""), ValNul())

tests/07_test_arrays__.py

@@ -0,0 +1,273 @@
+from tests._helpers import (
+  unittest, parameterized, Fraction, time,
+  run_test, run_compiler_error_test,
+  ArrayIndex, ArraySlice, Bool, BinOp, BuiltIn, DataArray, DataDict, DataRangeArray,
+  Defini, Continva, Designa, DesignaDestructure, DesignaIndex, DumStatement,
+  Erumpe, ExpressionStatement, Fvnctio, ID, InterpolatedString, Invoca,
+  ModuleCall, Nullus, Numeral, PerStatement, Program, Redi, SiStatement,
+  String, TemptaStatement, UnaryMinus, UnaryNot, Fractio, frac_to_fraction,
+  fraction_to_frac, num_to_int, int_to_num, make_string,
+  ValInt, ValStr, ValBool, ValList, ValDict, ValNul, ValFunc, ValFrac,
+  CentvrionError, _RUNTIME_C, _cent_rng,
+  Lexer, Parser, compile_program,
+  os, subprocess, tempfile, StringIO, patch,
+)
+
+
+# --- Array concatenation ---
+
+array_concat_tests = [
+  ("[I, II] @ [III, IV]",
+    Program([], [ExpressionStatement(BinOp(DataArray([Numeral("I"), Numeral("II")]), DataArray([Numeral("III"), Numeral("IV")]), "SYMBOL_AT"))]),
+    ValList([ValInt(1), ValInt(2), ValInt(3), ValInt(4)])),
+  ("[] @ [I]",
+    Program([], [ExpressionStatement(BinOp(DataArray([]), DataArray([Numeral("I")]), "SYMBOL_AT"))]),
+    ValList([ValInt(1)])),
+  ("[I] @ []",
+    Program([], [ExpressionStatement(BinOp(DataArray([Numeral("I")]), DataArray([]), "SYMBOL_AT"))]),
+    ValList([ValInt(1)])),
+  ("[] @ []",
+    Program([], [ExpressionStatement(BinOp(DataArray([]), DataArray([]), "SYMBOL_AT"))]),
+    ValList([])),
+  ('["a"] @ [I]',
+    Program([], [ExpressionStatement(BinOp(DataArray([String("a")]), DataArray([Numeral("I")]), "SYMBOL_AT"))]),
+    ValList([ValStr("a"), ValInt(1)])),
+  # left-associative chaining
+  ("[I] @ [II] @ [III]",
+    Program([], [ExpressionStatement(BinOp(BinOp(DataArray([Numeral("I")]), DataArray([Numeral("II")]), "SYMBOL_AT"), DataArray([Numeral("III")]), "SYMBOL_AT"))]),
+    ValList([ValInt(1), ValInt(2), ValInt(3)])),
+  # concat with variable
+  ("DESIGNA a VT [I, II]\nDESIGNA b VT [III]\na @ b",
+    Program([], [Designa(ID("a"), DataArray([Numeral("I"), Numeral("II")])), Designa(ID("b"), DataArray([Numeral("III")])), ExpressionStatement(BinOp(ID("a"), ID("b"), "SYMBOL_AT"))]),
+    ValList([ValInt(1), ValInt(2), ValInt(3)])),
+]
+
+class TestArrayConcat(unittest.TestCase):
+  @parameterized.expand(array_concat_tests)
+  def test_array_concat(self, source, nodes, value):
+    run_test(self, source, nodes, value)
+
+# --- Array indexing ---
+# Indexing is 1-based; I is the first element
+
+array_index_tests = [
+  # basic indexing
+  ("[I, II, III][I]", Program([], [ExpressionStatement(ArrayIndex(DataArray([Numeral("I"), Numeral("II"), Numeral("III")]), Numeral("I")))]), ValInt(1)),    # first element
+  ("[I, II, III][II]", Program([], [ExpressionStatement(ArrayIndex(DataArray([Numeral("I"), Numeral("II"), Numeral("III")]), Numeral("II")))]), ValInt(2)),   # second element
+  ("[I, II, III][III]", Program([], [ExpressionStatement(ArrayIndex(DataArray([Numeral("I"), Numeral("II"), Numeral("III")]), Numeral("III")))]), ValInt(3)),  # third element
+  # index into a variable
+  ("DESIGNA a VT [X, XX, XXX]\na[II]",
+    Program([], [Designa(ID("a"), DataArray([Numeral("X"), Numeral("XX"), Numeral("XXX")])), ExpressionStatement(ArrayIndex(ID("a"), Numeral("II")))]),
+    ValInt(20)),  # second element
+  # index into range array
+  ("[I VSQVE V][II]", Program([], [ExpressionStatement(ArrayIndex(DataRangeArray(Numeral("I"), Numeral("V")), Numeral("II")))]), ValInt(2)),      # second element of [1,2,3,4,5]
+  # expression as index
+  ("[I, II, III][I + I]",
+    Program([], [ExpressionStatement(ArrayIndex(
+      DataArray([Numeral("I"), Numeral("II"), Numeral("III")]),
+      BinOp(Numeral("I"), Numeral("I"), "SYMBOL_PLUS")))]),
+    ValInt(2)),
+  # division result as index (no FRACTIO): IV / II = 2
+  ("[X, XX, XXX][IV / II]",
+    Program([], [ExpressionStatement(ArrayIndex(
+      DataArray([Numeral("X"), Numeral("XX"), Numeral("XXX")]),
+      BinOp(Numeral("IV"), Numeral("II"), "SYMBOL_DIVIDE")))]),
+    ValInt(20)),
+  # whole-number fraction (from division) as index, with FRACTIO imported
+  ("CVM FRACTIO\n[X, XX, XXX][IV / II]",
+    Program([ModuleCall("FRACTIO")], [ExpressionStatement(ArrayIndex(
+      DataArray([Numeral("X"), Numeral("XX"), Numeral("XXX")]),
+      BinOp(Numeral("IV"), Numeral("II"), "SYMBOL_DIVIDE")))]),
+    ValInt(20)),
+]
+
+class TestArrayIndex(unittest.TestCase):
+  @parameterized.expand(array_index_tests)
+  def test_array_index(self, source, nodes, value):
+    run_test(self, source, nodes, value)
+
+# --- Array index assignment ---
+
+array_index_assign_tests = [
+  # assign to middle element
+  ("DESIGNA a VT [I, II, III]\nDESIGNA a[II] VT X\na[II]",
+    Program([], [
+      Designa(ID("a"), DataArray([Numeral("I"), Numeral("II"), Numeral("III")])),
+      DesignaIndex(ID("a"), [Numeral("II")], Numeral("X")),
+      ExpressionStatement(ArrayIndex(ID("a"), Numeral("II"))),
+    ]),
+    ValInt(10)),
+  # assign to first element
+  ("DESIGNA a VT [I, II, III]\nDESIGNA a[I] VT V\na[I]",
+    Program([], [
+      Designa(ID("a"), DataArray([Numeral("I"), Numeral("II"), Numeral("III")])),
+      DesignaIndex(ID("a"), [Numeral("I")], Numeral("V")),
+      ExpressionStatement(ArrayIndex(ID("a"), Numeral("I"))),
+    ]),
+    ValInt(5)),
+  # assign to last element
+  ("DESIGNA a VT [I, II, III]\nDESIGNA a[III] VT L\na[III]",
+    Program([], [
+      Designa(ID("a"), DataArray([Numeral("I"), Numeral("II"), Numeral("III")])),
+      DesignaIndex(ID("a"), [Numeral("III")], Numeral("L")),
+      ExpressionStatement(ArrayIndex(ID("a"), Numeral("III"))),
+    ]),
+    ValInt(50)),
+  # other elements unaffected
+  ("DESIGNA a VT [I, II, III]\nDESIGNA a[II] VT X\na[I]",
+    Program([], [
+      Designa(ID("a"), DataArray([Numeral("I"), Numeral("II"), Numeral("III")])),
+      DesignaIndex(ID("a"), [Numeral("II")], Numeral("X")),
+      ExpressionStatement(ArrayIndex(ID("a"), Numeral("I"))),
+    ]),
+    ValInt(1)),
+  # expression as index
+  ("DESIGNA a VT [I, II, III]\nDESIGNA i VT II\nDESIGNA a[i] VT X\na[II]",
+    Program([], [
+      Designa(ID("a"), DataArray([Numeral("I"), Numeral("II"), Numeral("III")])),
+      Designa(ID("i"), Numeral("II")),
+      DesignaIndex(ID("a"), [ID("i")], Numeral("X")),
+      ExpressionStatement(ArrayIndex(ID("a"), Numeral("II"))),
+    ]),
+    ValInt(10)),
+]
+
+class TestArrayIndexAssign(unittest.TestCase):
+  @parameterized.expand(array_index_assign_tests)
+  def test_array_index_assign(self, source, nodes, value):
+    run_test(self, source, nodes, value)
+
+# --- Multi-dimensional array index assignment ---
+
+multidim_assign_tests = [
+  # 2D array assignment
+  ("DESIGNA a VT [[I, II], [III, IV]]\nDESIGNA a[I][II] VT X\na[I][II]",
+    Program([], [
+      Designa(ID("a"), DataArray([DataArray([Numeral("I"), Numeral("II")]), DataArray([Numeral("III"), Numeral("IV")])])),
+      DesignaIndex(ID("a"), [Numeral("I"), Numeral("II")], Numeral("X")),
+      ExpressionStatement(ArrayIndex(ArrayIndex(ID("a"), Numeral("I")), Numeral("II"))),
+    ]),
+    ValInt(10)),
+  # other elements unaffected
+  ("DESIGNA a VT [[I, II], [III, IV]]\nDESIGNA a[I][II] VT X\na[II][I]",
+    Program([], [
+      Designa(ID("a"), DataArray([DataArray([Numeral("I"), Numeral("II")]), DataArray([Numeral("III"), Numeral("IV")])])),
+      DesignaIndex(ID("a"), [Numeral("I"), Numeral("II")], Numeral("X")),
+      ExpressionStatement(ArrayIndex(ArrayIndex(ID("a"), Numeral("II")), Numeral("I"))),
+    ]),
+    ValInt(3)),
+  # dict inside array
+  ('DESIGNA a VT [TABVLA {"x" VT I}]\nDESIGNA a[I]["x"] VT X\na[I]["x"]',
+    Program([], [
+      Designa(ID("a"), DataArray([DataDict([(String("x"), Numeral("I"))])])),
+      DesignaIndex(ID("a"), [Numeral("I"), String("x")], Numeral("X")),
+      ExpressionStatement(ArrayIndex(ArrayIndex(ID("a"), Numeral("I")), String("x"))),
+    ]),
+    ValInt(10)),
+  # array inside dict
+  ('DESIGNA d VT TABVLA {"a" VT [I, II]}\nDESIGNA d["a"][I] VT X\nd["a"][I]',
+    Program([], [
+      Designa(ID("d"), DataDict([(String("a"), DataArray([Numeral("I"), Numeral("II")]))])),
+      DesignaIndex(ID("d"), [String("a"), Numeral("I")], Numeral("X")),
+      ExpressionStatement(ArrayIndex(ArrayIndex(ID("d"), String("a")), Numeral("I"))),
+    ]),
+    ValInt(10)),
+  # 3 levels deep
+  ("DESIGNA a VT [[[I]]]\nDESIGNA a[I][I][I] VT X\na[I][I][I]",
+    Program([], [
+      Designa(ID("a"), DataArray([DataArray([DataArray([Numeral("I")])])])),
+      DesignaIndex(ID("a"), [Numeral("I"), Numeral("I"), Numeral("I")], Numeral("X")),
+      ExpressionStatement(ArrayIndex(ArrayIndex(ArrayIndex(ID("a"), Numeral("I")), Numeral("I")), Numeral("I"))),
+    ]),
+    ValInt(10)),
+]
+
+class TestMultidimAssign(unittest.TestCase):
+  @parameterized.expand(multidim_assign_tests)
+  def test_multidim_assign(self, source, nodes, value):
+    run_test(self, source, nodes, value)
+
+# --- Array slicing ---
+
+array_slice_tests = [
+  # basic slice from middle
+  ("[X, XX, XXX, XL, L][II VSQVE IV]",
+    Program([], [ExpressionStatement(ArraySlice(
+      DataArray([Numeral("X"), Numeral("XX"), Numeral("XXX"), Numeral("XL"), Numeral("L")]),
+      Numeral("II"), Numeral("IV")))]),
+    ValList([ValInt(20), ValInt(30), ValInt(40)])),
+  # slice of length 1
+  ("[I, II, III][II VSQVE II]",
+    Program([], [ExpressionStatement(ArraySlice(
+      DataArray([Numeral("I"), Numeral("II"), Numeral("III")]),
+      Numeral("II"), Numeral("II")))]),
+    ValList([ValInt(2)])),
+  # full array slice
+  ("[I, II, III][I VSQVE III]",
+    Program([], [ExpressionStatement(ArraySlice(
+      DataArray([Numeral("I"), Numeral("II"), Numeral("III")]),
+      Numeral("I"), Numeral("III")))]),
+    ValList([ValInt(1), ValInt(2), ValInt(3)])),
+  # slice on variable
+  ("DESIGNA a VT [I, II, III, IV, V]\na[II VSQVE IV]",
+    Program([], [
+      Designa(ID("a"), DataArray([Numeral("I"), Numeral("II"), Numeral("III"), Numeral("IV"), Numeral("V")])),
+      ExpressionStatement(ArraySlice(ID("a"), Numeral("II"), Numeral("IV"))),
+    ]),
+    ValList([ValInt(2), ValInt(3), ValInt(4)])),
+  # slice then index (chained)
+  ("[I, II, III, IV][I VSQVE III][II]",
+    Program([], [ExpressionStatement(ArrayIndex(
+      ArraySlice(
+        DataArray([Numeral("I"), Numeral("II"), Numeral("III"), Numeral("IV")]),
+        Numeral("I"), Numeral("III")),
+      Numeral("II")))]),
+    ValInt(2)),
+  # slice on range array
+  ("[I VSQVE X][III VSQVE VII]",
+    Program([], [ExpressionStatement(ArraySlice(
+      DataRangeArray(Numeral("I"), Numeral("X")),
+      Numeral("III"), Numeral("VII")))]),
+    ValList([ValInt(3), ValInt(4), ValInt(5), ValInt(6), ValInt(7)])),
+  # expression as slice bounds
+  ("[I, II, III, IV, V][I + I VSQVE II + II]",
+    Program([], [ExpressionStatement(ArraySlice(
+      DataArray([Numeral("I"), Numeral("II"), Numeral("III"), Numeral("IV"), Numeral("V")]),
+      BinOp(Numeral("I"), Numeral("I"), "SYMBOL_PLUS"),
+      BinOp(Numeral("II"), Numeral("II"), "SYMBOL_PLUS")))]),
+    ValList([ValInt(2), ValInt(3), ValInt(4)])),
+]
+
+class TestArraySlice(unittest.TestCase):
+  @parameterized.expand(array_slice_tests)
+  def test_array_slice(self, source, nodes, value):
+    run_test(self, source, nodes, value)
+
+# --- Multiline arrays ---
+
+multiline_array_tests = [
+  # newlines after commas
+  ("[I,\nII,\nIII]",
+    Program([], [ExpressionStatement(DataArray([Numeral("I"), Numeral("II"), Numeral("III")]))]),
+    ValList([ValInt(1), ValInt(2), ValInt(3)])),
+  # single newline after comma
+  ("[I, II,\nIII]",
+    Program([], [ExpressionStatement(DataArray([Numeral("I"), Numeral("II"), Numeral("III")]))]),
+    ValList([ValInt(1), ValInt(2), ValInt(3)])),
+  # empty array still works
+  ("[]",
+    Program([], [ExpressionStatement(DataArray([]))]),
+    ValList([])),
+  # nested arrays with newlines
+  ("[I,\n[II, III],\nIV]",
+    Program([], [ExpressionStatement(DataArray([
+      Numeral("I"),
+      DataArray([Numeral("II"), Numeral("III")]),
+      Numeral("IV")]))]),
+    ValList([ValInt(1), ValList([ValInt(2), ValInt(3)]), ValInt(4)])),
+]
+
+class TestMultilineArray(unittest.TestCase):
+  @parameterized.expand(multiline_array_tests)
+  def test_multiline_array(self, source, nodes, value):
+    run_test(self, source, nodes, value)

tests/08_test_tabulas_.py

@@ -0,0 +1,191 @@
+from tests._helpers import (
+  unittest, parameterized, Fraction, time,
+  run_test, run_compiler_error_test,
+  ArrayIndex, ArraySlice, Bool, BinOp, BuiltIn, DataArray, DataDict, DataRangeArray,
+  Defini, Continva, Designa, DesignaDestructure, DesignaIndex, DumStatement,
+  Erumpe, ExpressionStatement, Fvnctio, ID, InterpolatedString, Invoca,
+  ModuleCall, Nullus, Numeral, PerStatement, Program, Redi, SiStatement,
+  String, TemptaStatement, UnaryMinus, UnaryNot, Fractio, frac_to_fraction,
+  fraction_to_frac, num_to_int, int_to_num, make_string,
+  ValInt, ValStr, ValBool, ValList, ValDict, ValNul, ValFunc, ValFrac,
+  CentvrionError, _RUNTIME_C, _cent_rng,
+  Lexer, Parser, compile_program,
+  os, subprocess, tempfile, StringIO, patch,
+)
+
+
+# --- Dict (TABVLA) ---
+
+dict_tests = [
+  # empty dict
+  ("TABVLA {}",
+    Program([], [ExpressionStatement(DataDict([]))]),
+    ValDict({})),
+  # single string key
+  ('TABVLA {"a" VT I}',
+    Program([], [ExpressionStatement(DataDict([(String("a"), Numeral("I"))]))]),
+    ValDict({"a": ValInt(1)})),
+  # multiple entries
+  ('TABVLA {"a" VT I, "b" VT II}',
+    Program([], [ExpressionStatement(DataDict([(String("a"), Numeral("I")), (String("b"), Numeral("II"))]))]),
+    ValDict({"a": ValInt(1), "b": ValInt(2)})),
+  # integer keys
+  ('TABVLA {I VT "one", II VT "two"}',
+    Program([], [ExpressionStatement(DataDict([(Numeral("I"), String("one")), (Numeral("II"), String("two"))]))]),
+    ValDict({1: ValStr("one"), 2: ValStr("two")})),
+  # expression values
+  ('TABVLA {"x" VT I + II}',
+    Program([], [ExpressionStatement(DataDict([(String("x"), BinOp(Numeral("I"), Numeral("II"), "SYMBOL_PLUS"))]))]),
+    ValDict({"x": ValInt(3)})),
+  # empty dict with newline
+  ('TABVLA {\n}',
+    Program([], [ExpressionStatement(DataDict([]))]),
+    ValDict({})),
+  # single entry with surrounding newlines
+  ('TABVLA {\n"a" VT I\n}',
+    Program([], [ExpressionStatement(DataDict([(String("a"), Numeral("I"))]))]),
+    ValDict({"a": ValInt(1)})),
+  # multiple entries with newlines after commas
+  ('TABVLA {\n"a" VT I,\n"b" VT II\n}',
+    Program([], [ExpressionStatement(DataDict([(String("a"), Numeral("I")), (String("b"), Numeral("II"))]))]),
+    ValDict({"a": ValInt(1), "b": ValInt(2)})),
+  # newlines around every delimiter
+  ('TABVLA {\n"a" VT I,\n"b" VT II,\n"c" VT III\n}',
+    Program([], [ExpressionStatement(DataDict([(String("a"), Numeral("I")), (String("b"), Numeral("II")), (String("c"), Numeral("III"))]))]),
+    ValDict({"a": ValInt(1), "b": ValInt(2), "c": ValInt(3)})),
+]
+
+class TestDict(unittest.TestCase):
+  @parameterized.expand(dict_tests)
+  def test_dict(self, source, nodes, value):
+    run_test(self, source, nodes, value)
+
+
+dict_index_tests = [
+  # string key access
+  ('TABVLA {"a" VT X}["a"]',
+    Program([], [ExpressionStatement(ArrayIndex(DataDict([(String("a"), Numeral("X"))]), String("a")))]),
+    ValInt(10)),
+  # integer key access
+  ('TABVLA {I VT "one"}[I]',
+    Program([], [ExpressionStatement(ArrayIndex(DataDict([(Numeral("I"), String("one"))]), Numeral("I")))]),
+    ValStr("one")),
+  # access via variable
+  ('DESIGNA d VT TABVLA {"x" VT V}\nd["x"]',
+    Program([], [
+      Designa(ID("d"), DataDict([(String("x"), Numeral("V"))])),
+      ExpressionStatement(ArrayIndex(ID("d"), String("x"))),
+    ]),
+    ValInt(5)),
+  # nested dict access
+  ('TABVLA {"a" VT TABVLA {"b" VT X}}["a"]["b"]',
+    Program([], [ExpressionStatement(
+      ArrayIndex(ArrayIndex(DataDict([(String("a"), DataDict([(String("b"), Numeral("X"))]))]), String("a")), String("b"))
+    )]),
+    ValInt(10)),
+]
+
+class TestDictIndex(unittest.TestCase):
+  @parameterized.expand(dict_index_tests)
+  def test_dict_index(self, source, nodes, value):
+    run_test(self, source, nodes, value)
+
+
+dict_assign_tests = [
+  # update existing key
+  ('DESIGNA d VT TABVLA {"a" VT I}\nDESIGNA d["a"] VT X\nd["a"]',
+    Program([], [
+      Designa(ID("d"), DataDict([(String("a"), Numeral("I"))])),
+      DesignaIndex(ID("d"), [String("a")], Numeral("X")),
+      ExpressionStatement(ArrayIndex(ID("d"), String("a"))),
+    ]),
+    ValInt(10)),
+  # insert new key
+  ('DESIGNA d VT TABVLA {"a" VT I}\nDESIGNA d["b"] VT II\nd["b"]',
+    Program([], [
+      Designa(ID("d"), DataDict([(String("a"), Numeral("I"))])),
+      DesignaIndex(ID("d"), [String("b")], Numeral("II")),
+      ExpressionStatement(ArrayIndex(ID("d"), String("b"))),
+    ]),
+    ValInt(2)),
+  # original key unaffected after insert
+  ('DESIGNA d VT TABVLA {"a" VT I}\nDESIGNA d["b"] VT II\nd["a"]',
+    Program([], [
+      Designa(ID("d"), DataDict([(String("a"), Numeral("I"))])),
+      DesignaIndex(ID("d"), [String("b")], Numeral("II")),
+      ExpressionStatement(ArrayIndex(ID("d"), String("a"))),
+    ]),
+    ValInt(1)),
+]
+
+class TestDictAssign(unittest.TestCase):
+  @parameterized.expand(dict_assign_tests)
+  def test_dict_assign(self, source, nodes, value):
+    run_test(self, source, nodes, value)
+
+
+dict_builtin_tests = [
+  # LONGITVDO on dict
+  ('LONGITVDO(TABVLA {"a" VT I, "b" VT II})',
+    Program([], [ExpressionStatement(BuiltIn("LONGITVDO", [DataDict([(String("a"), Numeral("I")), (String("b"), Numeral("II"))])]))]),
+    ValInt(2)),
+  # LONGITVDO on empty dict
+  ('LONGITVDO(TABVLA {})',
+    Program([], [ExpressionStatement(BuiltIn("LONGITVDO", [DataDict([])]))]),
+    ValInt(0)),
+  # CLAVES
+  ('CLAVES(TABVLA {"a" VT I, "b" VT II})',
+    Program([], [ExpressionStatement(BuiltIn("CLAVES", [DataDict([(String("a"), Numeral("I")), (String("b"), Numeral("II"))])]))]),
+    ValList([ValStr("a"), ValStr("b")])),
+  # CLAVES with int keys
+  ('CLAVES(TABVLA {I VT "x", II VT "y"})',
+    Program([], [ExpressionStatement(BuiltIn("CLAVES", [DataDict([(Numeral("I"), String("x")), (Numeral("II"), String("y"))])]))]),
+    ValList([ValInt(1), ValInt(2)])),
+]
+
+class TestDictBuiltins(unittest.TestCase):
+  @parameterized.expand(dict_builtin_tests)
+  def test_dict_builtin(self, source, nodes, value):
+    run_test(self, source, nodes, value)
+
+
+dict_iteration_tests = [
+  # PER iterates over keys
+  ('DESIGNA r VT ""\nPER k IN TABVLA {"a" VT I, "b" VT II} FAC {\nDESIGNA r VT r & k\n}\nr',
+    Program([], [
+      Designa(ID("r"), String("")),
+      PerStatement(
+        DataDict([(String("a"), Numeral("I")), (String("b"), Numeral("II"))]),
+        ID("k"),
+        [Designa(ID("r"), BinOp(ID("r"), ID("k"), "SYMBOL_AMPERSAND"))],
+      ),
+      ExpressionStatement(ID("r")),
+    ]),
+    ValStr("ab")),
+]
+
+class TestDictIteration(unittest.TestCase):
+  @parameterized.expand(dict_iteration_tests)
+  def test_dict_iteration(self, source, nodes, value):
+    run_test(self, source, nodes, value)
+
+
+dict_display_tests = [
+  # DIC on dict
+  ('DIC(TABVLA {"a" VT I})',
+    Program([], [ExpressionStatement(BuiltIn("DIC", [DataDict([(String("a"), Numeral("I"))])]))]),
+    ValStr("{a VT I}"), "{a VT I}\n"),
+  # DIC on multi-entry dict
+  ('DIC(TABVLA {"a" VT I, "b" VT II})',
+    Program([], [ExpressionStatement(BuiltIn("DIC", [DataDict([(String("a"), Numeral("I")), (String("b"), Numeral("II"))])]))]),
+    ValStr("{a VT I, b VT II}"), "{a VT I, b VT II}\n"),
+  # DIC on empty dict
+  ('DIC(TABVLA {})',
+    Program([], [ExpressionStatement(BuiltIn("DIC", [DataDict([])]))]),
+    ValStr("{}"), "{}\n"),
+]
+
+class TestDictDisplay(unittest.TestCase):
+  @parameterized.expand(dict_display_tests)
+  def test_dict_display(self, source, nodes, value, output):
+    run_test(self, source, nodes, value, output)

tests/09_test_fraction.py

@@ -0,0 +1,263 @@
+from tests._helpers import (
+  unittest, parameterized, Fraction, time,
+  run_test, run_compiler_error_test,
+  ArrayIndex, ArraySlice, Bool, BinOp, BuiltIn, DataArray, DataDict, DataRangeArray,
+  Defini, Continva, Designa, DesignaDestructure, DesignaIndex, DumStatement,
+  Erumpe, ExpressionStatement, Fvnctio, ID, InterpolatedString, Invoca,
+  ModuleCall, Nullus, Numeral, PerStatement, Program, Redi, SiStatement,
+  String, TemptaStatement, UnaryMinus, UnaryNot, Fractio, frac_to_fraction,
+  fraction_to_frac, num_to_int, int_to_num, make_string,
+  ValInt, ValStr, ValBool, ValList, ValDict, ValNul, ValFunc, ValFrac,
+  CentvrionError, _RUNTIME_C, _cent_rng,
+  Lexer, Parser, compile_program,
+  os, subprocess, tempfile, StringIO, patch,
+)
+
+
+# --- FRACTIO module ---
+
+fractio_tests = [
+  # Basic fraction literals
+  ("CVM FRACTIO\nIIIS",
+    Program([ModuleCall("FRACTIO")], [ExpressionStatement(Fractio("IIIS"))]),
+    ValFrac(Fraction(7, 2))),
+  ("CVM FRACTIO\nS",
+    Program([ModuleCall("FRACTIO")], [ExpressionStatement(Fractio("S"))]),
+    ValFrac(Fraction(1, 2))),
+  ("CVM FRACTIO\nS:.",
+    Program([ModuleCall("FRACTIO")], [ExpressionStatement(Fractio("S:."))]),
+    ValFrac(Fraction(3, 4))),
+  ("CVM FRACTIO\n.",
+    Program([ModuleCall("FRACTIO")], [ExpressionStatement(Fractio("."))]),
+    ValFrac(Fraction(1, 12))),
+  ("CVM FRACTIO\n:.",
+    Program([ModuleCall("FRACTIO")], [ExpressionStatement(Fractio(":."))]),
+    ValFrac(Fraction(1, 4))),
+  # Integer part with fraction
+  ("CVM FRACTIO\nVIIS:|::",
+    Program([ModuleCall("FRACTIO")], [ExpressionStatement(Fractio("VIIS:|::"))]),
+    ValFrac(Fraction(7) + Fraction(100, 144))),
+  # Arithmetic
+  ("CVM FRACTIO\nIIIS + S",
+    Program([ModuleCall("FRACTIO")], [
+      ExpressionStatement(BinOp(Fractio("IIIS"), Fractio("S"), "SYMBOL_PLUS"))
+    ]),
+    ValFrac(Fraction(4))
+  ),
+  ("CVM FRACTIO\nIIIS - S",
+    Program([ModuleCall("FRACTIO")], [
+      ExpressionStatement(BinOp(Fractio("IIIS"), Fractio("S"), "SYMBOL_MINUS"))
+    ]),
+    ValFrac(Fraction(3))
+  ),
+  ("CVM FRACTIO\nS * IV",
+    Program([ModuleCall("FRACTIO")], [
+      ExpressionStatement(BinOp(Fractio("S"), Numeral("IV"), "SYMBOL_TIMES"))
+    ]),
+    ValFrac(Fraction(2))
+  ),
+  # Division returns fraction
+  ("CVM FRACTIO\nI / IV",
+    Program([ModuleCall("FRACTIO")], [
+      ExpressionStatement(BinOp(Numeral("I"), Numeral("IV"), "SYMBOL_DIVIDE"))
+    ]),
+    ValFrac(Fraction(1, 4))
+  ),
+  ("CVM FRACTIO\nI / III",
+    Program([ModuleCall("FRACTIO")], [
+      ExpressionStatement(BinOp(Numeral("I"), Numeral("III"), "SYMBOL_DIVIDE"))
+    ]),
+    ValFrac(Fraction(1, 3))
+  ),
+  # Integer division still works without fractions in operands... but with FRACTIO returns ValFrac
+  ("CVM FRACTIO\nX / II",
+    Program([ModuleCall("FRACTIO")], [
+      ExpressionStatement(BinOp(Numeral("X"), Numeral("II"), "SYMBOL_DIVIDE"))
+    ]),
+    ValFrac(Fraction(5))
+  ),
+  # Modulo on fractions: 7/2 RELIQVVM 3/2 = 1/2 (7/2 / 3/2 = 7/3, floor=2, 7/2 - 3 = 1/2)
+  ("CVM FRACTIO\nIIIS RELIQVVM IS",
+    Program([ModuleCall("FRACTIO")], [
+      ExpressionStatement(BinOp(Fractio("IIIS"), Fractio("IS"), "KEYWORD_RELIQVVM"))
+    ]),
+    ValFrac(Fraction(1, 2))
+  ),
+  # Modulo with mixed operand types: 5/2 RELIQVVM 1 = 1/2
+  ("CVM FRACTIO\nIIS RELIQVVM I",
+    Program([ModuleCall("FRACTIO")], [
+      ExpressionStatement(BinOp(Fractio("IIS"), Numeral("I"), "KEYWORD_RELIQVVM"))
+    ]),
+    ValFrac(Fraction(1, 2))
+  ),
+  # Int operands under FRACTIO still return a fraction: 10 RELIQVVM 3 = 1 (as Fraction)
+  ("CVM FRACTIO\nX RELIQVVM III",
+    Program([ModuleCall("FRACTIO")], [
+      ExpressionStatement(BinOp(Numeral("X"), Numeral("III"), "KEYWORD_RELIQVVM"))
+    ]),
+    ValFrac(Fraction(1))
+  ),
+  # Exact multiple under FRACTIO: 3 RELIQVVM 3/2 = 0
+  ("CVM FRACTIO\nIII RELIQVVM IS",
+    Program([ModuleCall("FRACTIO")], [
+      ExpressionStatement(BinOp(Numeral("III"), Fractio("IS"), "KEYWORD_RELIQVVM"))
+    ]),
+    ValFrac(Fraction(0))
+  ),
+  # String concatenation with fraction
+  ("CVM FRACTIO\nDIC(IIIS & \"!\")",
+    Program([ModuleCall("FRACTIO")], [
+      ExpressionStatement(BuiltIn("DIC", [BinOp(Fractio("IIIS"), String("!"), "SYMBOL_AMPERSAND")]))
+    ]),
+    ValStr("IIIS!"), "IIIS!\n"
+  ),
+  # Negative fractions
+  ("CVM FRACTIO\nCVM SVBNVLLA\n-IIS",
+    Program([ModuleCall("FRACTIO"),ModuleCall("SVBNVLLA")],[
+      ExpressionStatement(UnaryMinus(Fractio("IIS")))
+    ]),
+    ValFrac(Fraction(-5,2))
+  )
+]
+
+class TestFractio(unittest.TestCase):
+  @parameterized.expand(fractio_tests)
+  def test_fractio(self, source, nodes, value, output=""):
+    run_test(self, source, nodes, value, output)
+
+
+fractio_comparison_tests = [
+  # fraction vs fraction
+  ("CVM FRACTIO\nIIIS PLVS III",
+    Program([ModuleCall("FRACTIO")], [
+      ExpressionStatement(BinOp(Fractio("IIIS"), Numeral("III"), "KEYWORD_PLVS"))
+    ]),
+    ValBool(True)
+  ),
+  ("CVM FRACTIO\nIII MINVS IIIS",
+    Program([ModuleCall("FRACTIO")], [
+      ExpressionStatement(BinOp(Numeral("III"), Fractio("IIIS"), "KEYWORD_MINVS"))
+    ]),
+    ValBool(True)
+  ),
+  ("CVM FRACTIO\nIIIS MINVS IV",
+    Program([ModuleCall("FRACTIO")], [
+      ExpressionStatement(BinOp(Fractio("IIIS"), Numeral("IV"), "KEYWORD_MINVS"))
+    ]),
+    ValBool(True)
+  ),
+  ("CVM FRACTIO\nIV PLVS IIIS",
+    Program([ModuleCall("FRACTIO")], [
+      ExpressionStatement(BinOp(Numeral("IV"), Fractio("IIIS"), "KEYWORD_PLVS"))
+    ]),
+    ValBool(True)
+  ),
+  ("CVM FRACTIO\nIIIS PLVS IIIS",
+    Program([ModuleCall("FRACTIO")], [
+      ExpressionStatement(BinOp(Fractio("IIIS"), Fractio("IIIS"), "KEYWORD_PLVS"))
+    ]),
+    ValBool(False)
+  ),
+  ("CVM FRACTIO\nIIIS MINVS IIIS",
+    Program([ModuleCall("FRACTIO")], [
+      ExpressionStatement(BinOp(Fractio("IIIS"), Fractio("IIIS"), "KEYWORD_MINVS"))
+    ]),
+    ValBool(False)
+  ),
+  # HAVD_PLVS / HAVD_MINVS on fractions — equality boundary distinguishes from MINVS / PLVS
+  ("CVM FRACTIO\nIIIS HAVD_PLVS III",
+    Program([ModuleCall("FRACTIO")], [
+      ExpressionStatement(BinOp(Fractio("IIIS"), Numeral("III"), "KEYWORD_HAVD_PLVS"))
+    ]),
+    ValBool(False)  # 3.5 <= 3 is false
+  ),
+  ("CVM FRACTIO\nIIIS HAVD_MINVS IIIS",
+    Program([ModuleCall("FRACTIO")], [
+      ExpressionStatement(BinOp(Fractio("IIIS"), Fractio("IIIS"), "KEYWORD_HAVD_MINVS"))
+    ]),
+    ValBool(True)  # 3.5 >= 3.5 is true (equality boundary)
+  ),
+  ("CVM FRACTIO\nIIIS HAVD_PLVS IIIS",
+    Program([ModuleCall("FRACTIO")], [
+      ExpressionStatement(BinOp(Fractio("IIIS"), Fractio("IIIS"), "KEYWORD_HAVD_PLVS"))
+    ]),
+    ValBool(True)  # 3.5 <= 3.5 is true (equality boundary)
+  ),
+  # equality: fraction == fraction
+  ("CVM FRACTIO\nIIIS EST IIIS",
+    Program([ModuleCall("FRACTIO")], [
+      ExpressionStatement(BinOp(Fractio("IIIS"), Fractio("IIIS"), "KEYWORD_EST"))
+    ]),
+    ValBool(True)
+  ),
+  ("CVM FRACTIO\nIIIS EST IV",
+    Program([ModuleCall("FRACTIO")], [
+      ExpressionStatement(BinOp(Fractio("IIIS"), Numeral("IV"), "KEYWORD_EST"))
+    ]),
+    ValBool(False)
+  ),
+  # equality: fraction == whole number (ValFrac(4) vs ValInt(4))
+  ("CVM FRACTIO\nIIIS + S EST IV",
+    Program([ModuleCall("FRACTIO")], [
+      ExpressionStatement(BinOp(
+        BinOp(Fractio("IIIS"), Fractio("S"), "SYMBOL_PLUS"),
+        Numeral("IV"), "KEYWORD_EST"))
+    ]),
+    ValBool(True)
+  ),
+  ("CVM FRACTIO\nS + S EST I",
+    Program([ModuleCall("FRACTIO")], [
+      ExpressionStatement(BinOp(
+        BinOp(Fractio("S"), Fractio("S"), "SYMBOL_PLUS"),
+        Numeral("I"), "KEYWORD_EST"))
+    ]),
+    ValBool(True)
+  ),
+]
+
+class TestFractioComparisons(unittest.TestCase):
+  @parameterized.expand(fractio_comparison_tests)
+  def test_fractio_comparison(self, source, nodes, value):
+    run_test(self, source, nodes, value)
+
+
+class TestFractioHelpers(unittest.TestCase):
+  def test_frac_to_fraction_ordering(self):
+    with self.assertRaises(CentvrionError):
+      frac_to_fraction(".S")  # . before S violates highest-to-lowest
+
+  def test_frac_to_fraction_level_overflow(self):
+    with self.assertRaises(CentvrionError):
+      frac_to_fraction("SSSSSS")  # SS means S twice = 12/12 = 1, violating < 12/12 constraint
+
+  def test_frac_to_fraction_iiis(self):
+    self.assertEqual(frac_to_fraction("IIIS"), Fraction(7, 2))
+
+  def test_frac_to_fraction_s_colon_dot(self):
+    self.assertEqual(frac_to_fraction("S:."), Fraction(3, 4))
+
+  def test_frac_to_fraction_dot(self):
+    self.assertEqual(frac_to_fraction("."), Fraction(1, 12))
+
+  def test_frac_to_fraction_multilevel(self):
+    self.assertEqual(frac_to_fraction("VIIS:|::"), Fraction(7) + Fraction(100, 144))
+
+  def test_fraction_to_frac_iiis(self):
+    self.assertEqual(fraction_to_frac(Fraction(7, 2)), "IIIS")
+
+  def test_fraction_to_frac_s_colon_dot(self):
+    self.assertEqual(fraction_to_frac(Fraction(3, 4)), "S:.")
+
+  def test_fraction_to_frac_dot(self):
+    self.assertEqual(fraction_to_frac(Fraction(1, 12)), ".")
+
+  def test_fraction_to_frac_multilevel(self):
+    self.assertEqual(
+      fraction_to_frac(Fraction(7) + Fraction(100, 144)),
+      "VIIS:|::"
+    )
+
+  def test_roundtrip(self):
+    # Only canonical forms roundtrip — fraction_to_frac always uses max colons before dots
+    for s in ["IIIS", "S:.", ".", "::", "VIIS:|::", "S"]:
+      self.assertEqual(fraction_to_frac(frac_to_fraction(s)), s)

tests/10_test_external.py

@@ -0,0 +1,406 @@
+from tests._helpers import (
+  unittest, parameterized, Fraction, time,
+  run_test, run_compiler_error_test,
+  ArrayIndex, ArraySlice, Bool, BinOp, BuiltIn, DataArray, DataDict, DataRangeArray,
+  Defini, Continva, Designa, DesignaDestructure, DesignaIndex, DumStatement,
+  Erumpe, ExpressionStatement, Fvnctio, ID, InterpolatedString, Invoca,
+  ModuleCall, Nullus, Numeral, PerStatement, Program, Redi, SiStatement,
+  String, TemptaStatement, UnaryMinus, UnaryNot, Fractio, frac_to_fraction,
+  fraction_to_frac, num_to_int, int_to_num, make_string,
+  ValInt, ValStr, ValBool, ValList, ValDict, ValNul, ValFunc, ValFrac,
+  CentvrionError, _RUNTIME_C, _cent_rng,
+  Lexer, Parser, compile_program,
+  os, subprocess, tempfile, StringIO, patch,
+)
+
+
+# --- DORMI ---
+
+dormi_tests = [
+  ("DORMI(NVLLVS)",
+    Program([], [ExpressionStatement(BuiltIn("DORMI", [Nullus()]))]),
+    ValNul()),
+]
+
+class TestDormi(unittest.TestCase):
+  @parameterized.expand(dormi_tests)
+  def test_dormi(self, source, nodes, value, output=""):
+    run_test(self, source, nodes, value, output)
+
+  def test_dormi_timing_int(self):
+    source = "DORMI(I)\n"
+    lexer = Lexer().get_lexer()
+    tokens = lexer.lex(source)
+    program = Parser().parse(tokens)
+
+    start = time.time()
+    program.eval()
+    elapsed = time.time() - start
+    self.assertAlmostEqual(elapsed, 1.0, delta=0.5)
+
+  def test_dormi_timing_int_compiled(self):
+    source = "DORMI(I)\n"
+    lexer = Lexer().get_lexer()
+    tokens = lexer.lex(source)
+    program = Parser().parse(tokens)
+
+    c_source = compile_program(program)
+    with tempfile.NamedTemporaryFile(suffix=".c", delete=False, mode="w") as tmp_c:
+      tmp_c.write(c_source)
+      tmp_c_path = tmp_c.name
+    with tempfile.NamedTemporaryFile(suffix="", delete=False) as tmp_bin:
+      tmp_bin_path = tmp_bin.name
+    try:
+      subprocess.run(
+        ["gcc", "-O2", tmp_c_path, _RUNTIME_C, "-o", tmp_bin_path, "-lcurl", "-lmicrohttpd"],
+        check=True, capture_output=True,
+      )
+      start = time.time()
+      proc = subprocess.run([tmp_bin_path], capture_output=True, text=True)
+      elapsed = time.time() - start
+      self.assertEqual(proc.returncode, 0)
+      self.assertAlmostEqual(elapsed, 1.0, delta=0.5)
+    finally:
+      os.unlink(tmp_c_path)
+      os.unlink(tmp_bin_path)
+
+  def test_dormi_timing_frac(self):
+    source = "CVM FRACTIO\nDORMI(S)\n"
+    lexer = Lexer().get_lexer()
+    tokens = lexer.lex(source)
+    program = Parser().parse(tokens)
+
+    start = time.time()
+    program.eval()
+    elapsed = time.time() - start
+    self.assertAlmostEqual(elapsed, 0.5, delta=0.5)
+
+  def test_dormi_timing_frac_compiled(self):
+    source = "CVM FRACTIO\nDORMI(S)\n"
+    lexer = Lexer().get_lexer()
+    tokens = lexer.lex(source)
+    program = Parser().parse(tokens)
+
+    c_source = compile_program(program)
+    with tempfile.NamedTemporaryFile(suffix=".c", delete=False, mode="w") as tmp_c:
+      tmp_c.write(c_source)
+      tmp_c_path = tmp_c.name
+    with tempfile.NamedTemporaryFile(suffix="", delete=False) as tmp_bin:
+      tmp_bin_path = tmp_bin.name
+    try:
+      subprocess.run(
+        ["gcc", "-O2", tmp_c_path, _RUNTIME_C, "-o", tmp_bin_path, "-lcurl", "-lmicrohttpd"],
+        check=True, capture_output=True,
+      )
+      start = time.time()
+      proc = subprocess.run([tmp_bin_path], capture_output=True, text=True)
+      elapsed = time.time() - start
+      self.assertEqual(proc.returncode, 0)
+      self.assertAlmostEqual(elapsed, 0.5, delta=0.5)
+    finally:
+      os.unlink(tmp_c_path)
+      os.unlink(tmp_bin_path)
+
+class TestScripta(unittest.TestCase):
+  def _run_scripta(self, source):
+    lexer = Lexer().get_lexer()
+    tokens = lexer.lex(source + "\n")
+    program = Parser().parse(tokens)
+    # printer round-trip
+    new_text = program.print()
+    new_tokens = Lexer().get_lexer().lex(new_text + "\n")
+    new_nodes = Parser().parse(new_tokens)
+    self.assertEqual(program, new_nodes, f"Printer test\n{source}\n{new_text}")
+    return program
+
+  def _compile_and_run(self, program):
+    c_source = compile_program(program)
+    with tempfile.NamedTemporaryFile(suffix=".c", delete=False, mode="w") as tmp_c:
+      tmp_c.write(c_source)
+      tmp_c_path = tmp_c.name
+    with tempfile.NamedTemporaryFile(suffix="", delete=False) as tmp_bin:
+      tmp_bin_path = tmp_bin.name
+    try:
+      subprocess.run(
+        ["gcc", "-O2", tmp_c_path, _RUNTIME_C, "-o", tmp_bin_path, "-lcurl", "-lmicrohttpd"],
+        check=True, capture_output=True,
+      )
+      proc = subprocess.run([tmp_bin_path], capture_output=True, text=True)
+      self.assertEqual(proc.returncode, 0, f"Compiler binary exited non-zero:\n{proc.stderr}")
+      return proc.stdout
+    finally:
+      os.unlink(tmp_c_path)
+      os.unlink(tmp_bin_path)
+
+  def test_scribe_and_lege(self):
+    with tempfile.NamedTemporaryFile(suffix=".txt", delete=False) as f:
+      path = f.name
+    try:
+      source = f'CVM SCRIPTA\nSCRIBE("{path}", "SALVE MVNDE")\nDIC(LEGE("{path}"))'
+      program = self._run_scripta(source)
+      captured = StringIO()
+      with patch("sys.stdout", captured):
+        program.eval()
+      self.assertEqual(captured.getvalue(), "SALVE MVNDE\n")
+      with open(path) as f:
+        self.assertEqual(f.read(), "SALVE MVNDE")
+    finally:
+      if os.path.exists(path):
+        os.unlink(path)
+
+  def test_scribe_and_lege_compiled(self):
+    with tempfile.NamedTemporaryFile(suffix=".txt", delete=False) as f:
+      path = f.name
+    try:
+      source = f'CVM SCRIPTA\nSCRIBE("{path}", "SALVE MVNDE")\nDIC(LEGE("{path}"))'
+      program = self._run_scripta(source)
+      output = self._compile_and_run(program)
+      self.assertEqual(output, "SALVE MVNDE\n")
+      with open(path) as f:
+        self.assertEqual(f.read(), "SALVE MVNDE")
+    finally:
+      if os.path.exists(path):
+        os.unlink(path)
+
+  def test_adivnge(self):
+    with tempfile.NamedTemporaryFile(suffix=".txt", delete=False) as f:
+      path = f.name
+    try:
+      source = f'CVM SCRIPTA\nSCRIBE("{path}", "SALVE")\nADIVNGE("{path}", " MVNDE")\nDIC(LEGE("{path}"))'
+      program = self._run_scripta(source)
+      captured = StringIO()
+      with patch("sys.stdout", captured):
+        program.eval()
+      self.assertEqual(captured.getvalue(), "SALVE MVNDE\n")
+    finally:
+      if os.path.exists(path):
+        os.unlink(path)
+
+  def test_adivnge_compiled(self):
+    with tempfile.NamedTemporaryFile(suffix=".txt", delete=False) as f:
+      path = f.name
+    try:
+      source = f'CVM SCRIPTA\nSCRIBE("{path}", "SALVE")\nADIVNGE("{path}", " MVNDE")\nDIC(LEGE("{path}"))'
+      program = self._run_scripta(source)
+      output = self._compile_and_run(program)
+      self.assertEqual(output, "SALVE MVNDE\n")
+    finally:
+      if os.path.exists(path):
+        os.unlink(path)
+
+  def test_scribe_overwrites(self):
+    with tempfile.NamedTemporaryFile(suffix=".txt", delete=False) as f:
+      path = f.name
+    try:
+      source = f'CVM SCRIPTA\nSCRIBE("{path}", "first")\nSCRIBE("{path}", "second")\nLEGE("{path}")'
+      program = self._run_scripta(source)
+      result = program.eval()
+      self.assertEqual(result, ValStr("second"))
+    finally:
+      if os.path.exists(path):
+        os.unlink(path)
+
+  def test_lege_empty_file(self):
+    with tempfile.NamedTemporaryFile(suffix=".txt", delete=False, mode="w") as f:
+      path = f.name
+    try:
+      source = f'CVM SCRIPTA\nLEGE("{path}")'
+      program = self._run_scripta(source)
+      result = program.eval()
+      self.assertEqual(result, ValStr(""))
+    finally:
+      os.unlink(path)
+
+  def test_lege_preexisting_content(self):
+    with tempfile.NamedTemporaryFile(suffix=".txt", delete=False, mode="w") as f:
+      f.write("hello from python")
+      path = f.name
+    try:
+      source = f'CVM SCRIPTA\nLEGE("{path}")'
+      program = self._run_scripta(source)
+      result = program.eval()
+      self.assertEqual(result, ValStr("hello from python"))
+    finally:
+      os.unlink(path)
+
+  def test_scribe_returns_nullus(self):
+    with tempfile.NamedTemporaryFile(suffix=".txt", delete=False) as f:
+      path = f.name
+    try:
+      source = f'CVM SCRIPTA\nSCRIBE("{path}", "x")'
+      program = self._run_scripta(source)
+      result = program.eval()
+      self.assertEqual(result, ValNul())
+    finally:
+      if os.path.exists(path):
+        os.unlink(path)
+
+  def test_adivnge_returns_nullus(self):
+    with tempfile.NamedTemporaryFile(suffix=".txt", delete=False) as f:
+      path = f.name
+    try:
+      source = f'CVM SCRIPTA\nADIVNGE("{path}", "x")'
+      program = self._run_scripta(source)
+      result = program.eval()
+      self.assertEqual(result, ValNul())
+    finally:
+      if os.path.exists(path):
+        os.unlink(path)
+
+class TestRete(unittest.TestCase):
+  @classmethod
+  def setUpClass(cls):
+    import http.server, threading
+    class Handler(http.server.BaseHTTPRequestHandler):
+      def do_GET(self):
+        self.send_response(200)
+        self.send_header("Content-Type", "text/plain")
+        self.end_headers()
+        self.wfile.write(b"SALVE MVNDE")
+      def log_message(self, *args):
+        pass
+    cls.server = http.server.HTTPServer(("127.0.0.1", 0), Handler)
+    cls.port = cls.server.server_address[1]
+    cls.thread = threading.Thread(target=cls.server.serve_forever)
+    cls.thread.daemon = True
+    cls.thread.start()
+
+  @classmethod
+  def tearDownClass(cls):
+    cls.server.shutdown()
+
+  def test_pete(self):
+    url = f"http://127.0.0.1:{self.port}/"
+    source = f'CVM RETE\nPETE("{url}")'
+    run_test(self, source,
+      Program([ModuleCall("RETE")], [ExpressionStatement(BuiltIn("PETE", [String(url)]))]),
+      ValStr("SALVE MVNDE"))
+
+  def test_pete_dic(self):
+    url = f"http://127.0.0.1:{self.port}/"
+    source = f'CVM RETE\nDIC(PETE("{url}"))'
+    run_test(self, source,
+      Program([ModuleCall("RETE")], [ExpressionStatement(BuiltIn("DIC", [BuiltIn("PETE", [String(url)])]))]),
+      ValStr("SALVE MVNDE"), "SALVE MVNDE\n")
+
+class TestReteServer(unittest.TestCase):
+  """Integration tests for PETITVR + AVSCVLTA server functionality."""
+
+  def _wait_for_server(self, port, timeout=2.0):
+    """Poll until the server is accepting connections."""
+    import socket
+    deadline = time.time() + timeout
+    while time.time() < deadline:
+      try:
+        with socket.create_connection(("127.0.0.1", port), timeout=0.1):
+          return
+      except OSError:
+        time.sleep(0.05)
+    self.fail(f"Server on port {port} did not start within {timeout}s")
+
+  def _free_port(self):
+    """Find a free port in range 1024-3999 (representable without MAGNVM)."""
+    import socket, random
+    for _ in range(100):
+      port = random.randint(1024, 3999)
+      try:
+        with socket.socket() as s:
+          s.bind(("127.0.0.1", port))
+          return port
+      except OSError:
+        continue
+    raise RuntimeError("Could not find a free port in range 1024-3999")
+
+  def _run_server(self, source):
+    """Parse and eval source in a daemon thread. Returns when server is ready."""
+    import threading
+    lexer = Lexer().get_lexer()
+    tokens = lexer.lex(source + "\n")
+    program = Parser().parse(tokens)
+    t = threading.Thread(target=program.eval, daemon=True)
+    t.start()
+
+  def test_basic_handler(self):
+    port = self._free_port()
+    source = (
+      f'CVM RETE\n'
+      f'PETITVR("/", FVNCTIO (petitio) VT {{\n'
+      f'REDI("SALVE MVNDE")\n'
+      f'}})\n'
+      f'AVSCVLTA({int_to_num(port, False)})'
+    )
+    self._run_server(source)
+    self._wait_for_server(port)
+    import urllib.request
+    resp = urllib.request.urlopen(f"http://127.0.0.1:{port}/")
+    self.assertEqual(resp.read().decode(), "SALVE MVNDE")
+
+  def test_multiple_routes(self):
+    port = self._free_port()
+    source = (
+      f'CVM RETE\n'
+      f'PETITVR("/", FVNCTIO (p) VT {{\nREDI("RADIX")\n}})\n'
+      f'PETITVR("/nomen", FVNCTIO (p) VT {{\nREDI("MARCVS")\n}})\n'
+      f'AVSCVLTA({int_to_num(port, False)})'
+    )
+    self._run_server(source)
+    self._wait_for_server(port)
+    import urllib.request
+    resp1 = urllib.request.urlopen(f"http://127.0.0.1:{port}/")
+    self.assertEqual(resp1.read().decode(), "RADIX")
+    resp2 = urllib.request.urlopen(f"http://127.0.0.1:{port}/nomen")
+    self.assertEqual(resp2.read().decode(), "MARCVS")
+
+  def test_404_unmatched(self):
+    port = self._free_port()
+    source = (
+      f'CVM RETE\n'
+      f'PETITVR("/", FVNCTIO (p) VT {{\nREDI("ok")\n}})\n'
+      f'AVSCVLTA({int_to_num(port, False)})'
+    )
+    self._run_server(source)
+    self._wait_for_server(port)
+    import urllib.request, urllib.error
+    with self.assertRaises(urllib.error.HTTPError) as ctx:
+      urllib.request.urlopen(f"http://127.0.0.1:{port}/nonexistent")
+    self.assertEqual(ctx.exception.code, 404)
+
+  def test_request_dict_via(self):
+    port = self._free_port()
+    source = (
+      f'CVM RETE\n'
+      f'PETITVR("/echo", FVNCTIO (petitio) VT {{\n'
+      f'REDI(petitio["via"])\n'
+      f'}})\n'
+      f'AVSCVLTA({int_to_num(port, False)})'
+    )
+    self._run_server(source)
+    self._wait_for_server(port)
+    import urllib.request
+    resp = urllib.request.urlopen(f"http://127.0.0.1:{port}/echo")
+    self.assertEqual(resp.read().decode(), "/echo")
+
+  def test_request_dict_quaestio(self):
+    port = self._free_port()
+    source = (
+      f'CVM RETE\n'
+      f'PETITVR("/q", FVNCTIO (petitio) VT {{\n'
+      f'REDI(petitio["quaestio"])\n'
+      f'}})\n'
+      f'AVSCVLTA({int_to_num(port, False)})'
+    )
+    self._run_server(source)
+    self._wait_for_server(port)
+    import urllib.request
+    resp = urllib.request.urlopen(f"http://127.0.0.1:{port}/q?nomen=Marcus")
+    self.assertEqual(resp.read().decode(), "nomen=Marcus")
+
+  def test_petitvr_stores_route(self):
+    """PETITVR alone (without AVSCVLTA) just stores a route and returns NVLLVS."""
+    source = 'CVM RETE\nPETITVR("/", FVNCTIO (p) VT {\nREDI("hi")\n})'
+    run_test(self, source,
+      Program([ModuleCall("RETE")], [ExpressionStatement(BuiltIn("PETITVR", [
+        String("/"),
+        Fvnctio([ID("p")], [Redi([String("hi")])])
+      ]))]),
+      ValNul())

tests/11_test_assorted.py

@@ -0,0 +1,443 @@
+from tests._helpers import (
+  unittest, parameterized, Fraction, time,
+  run_test, run_compiler_error_test,
+  ArrayIndex, ArraySlice, Bool, BinOp, BuiltIn, DataArray, DataDict, DataRangeArray,
+  Defini, Continva, Designa, DesignaDestructure, DesignaIndex, DumStatement,
+  Erumpe, ExpressionStatement, Fvnctio, ID, InterpolatedString, Invoca,
+  ModuleCall, Nullus, Numeral, PerStatement, Program, Redi, SiStatement,
+  String, TemptaStatement, UnaryMinus, UnaryNot, Fractio, frac_to_fraction,
+  fraction_to_frac, num_to_int, int_to_num, make_string,
+  ValInt, ValStr, ValBool, ValList, ValDict, ValNul, ValFunc, ValFrac,
+  CentvrionError, _RUNTIME_C, _cent_rng,
+  Lexer, Parser, compile_program,
+  os, subprocess, tempfile, StringIO, patch,
+)
+
+
+# --- Comments ---
+
+comment_tests = [
+  # trailing line comment
+  ('DIC("hello") // this is ignored', Program([], [ExpressionStatement(BuiltIn("DIC", [String("hello")]))]), ValStr("hello"), "hello\n"),
+  # line comment on its own line before code
+  ('// ignored\nDIC("hi")', Program([], [ExpressionStatement(BuiltIn("DIC", [String("hi")]))]), ValStr("hi"), "hi\n"),
+  # inline block comment
+  ('DIC(/* ignored */ "hi")', Program([], [ExpressionStatement(BuiltIn("DIC", [String("hi")]))]), ValStr("hi"), "hi\n"),
+  # block comment spanning multiple lines
+  ('/* line one\nline two */\nDIC("hi")', Program([], [ExpressionStatement(BuiltIn("DIC", [String("hi")]))]), ValStr("hi"), "hi\n"),
+  # block comment mid-expression
+  ("II /* ignored */ + III", Program([], [ExpressionStatement(BinOp(Numeral("II"), Numeral("III"), "SYMBOL_PLUS"))]), ValInt(5)),
+  # line comment after expression (no output)
+  ("II + III // ignored", Program([], [ExpressionStatement(BinOp(Numeral("II"), Numeral("III"), "SYMBOL_PLUS"))]), ValInt(5)),
+  # division still works (/ token not confused with //)
+  ("X / II", Program([], [ExpressionStatement(BinOp(Numeral("X"), Numeral("II"), "SYMBOL_DIVIDE"))]), ValInt(5)),
+  # multiple line comments
+  ('// first\n// second\nDIC("ok")', Program([], [ExpressionStatement(BuiltIn("DIC", [String("ok")]))]), ValStr("ok"), "ok\n"),
+  # comment-only line between two statements
+  ('DESIGNA x VT I\n// set y\nDESIGNA y VT II\nx + y',
+    Program([], [Designa(ID("x"), Numeral("I")), Designa(ID("y"), Numeral("II")), ExpressionStatement(BinOp(ID("x"), ID("y"), "SYMBOL_PLUS"))]),
+    ValInt(3)),
+  # blank line between two statements (double newline)
+  ('DESIGNA x VT I\n\nDESIGNA y VT II\nx + y',
+    Program([], [Designa(ID("x"), Numeral("I")), Designa(ID("y"), Numeral("II")), ExpressionStatement(BinOp(ID("x"), ID("y"), "SYMBOL_PLUS"))]),
+    ValInt(3)),
+  # multiple comment-only lines between statements
+  ('DESIGNA x VT I\n// one\n// two\nDESIGNA y VT III\nx + y',
+    Program([], [Designa(ID("x"), Numeral("I")), Designa(ID("y"), Numeral("III")), ExpressionStatement(BinOp(ID("x"), ID("y"), "SYMBOL_PLUS"))]),
+    ValInt(4)),
+]
+
+class TestComments(unittest.TestCase):
+  @parameterized.expand(comment_tests)
+  def test_comments(self, source, nodes, value, output=""):
+    run_test(self, source, nodes, value, output)
+
+# --- Scope ---
+
+scope_tests = [
+  # SI: variable assigned in true branch persists in outer scope
+  ("SI VERITAS TVNC { DESIGNA r VT X }\nr",
+    Program([], [SiStatement(Bool(True), [Designa(ID("r"), Numeral("X"))], None), ExpressionStatement(ID("r"))]),
+    ValInt(10)),
+  # SI: variable assigned in ALIVD branch persists in outer scope
+  ("SI FALSITAS TVNC { DESIGNA r VT X } ALIVD { DESIGNA r VT V }\nr",
+    Program([], [SiStatement(Bool(False), [Designa(ID("r"), Numeral("X"))], [Designa(ID("r"), Numeral("V"))]), ExpressionStatement(ID("r"))]),
+    ValInt(5)),
+  # DVM: variable assigned in body persists after loop exits
+  # x goes 1→2→3→4→5; r tracks x each iteration; loop exits when x==5
+  ("DESIGNA x VT I\nDVM x EST V FAC { DESIGNA x VT x + I\nDESIGNA r VT x }\nr",
+    Program([], [
+      Designa(ID("x"), Numeral("I")),
+      DumStatement(BinOp(ID("x"), Numeral("V"), "KEYWORD_EST"), [
+        Designa(ID("x"), BinOp(ID("x"), Numeral("I"), "SYMBOL_PLUS")),
+        Designa(ID("r"), ID("x")),
+      ]),
+      ExpressionStatement(ID("r")),
+    ]),
+    ValInt(5)),
+  # PER: loop variable holds last array element after loop (no ERVMPE)
+  ("PER i IN [I, II, III] FAC { DESIGNA nop VT I }\ni",
+    Program([], [
+      PerStatement(DataArray([Numeral("I"), Numeral("II"), Numeral("III")]), ID("i"), [Designa(ID("nop"), Numeral("I"))]),
+      ExpressionStatement(ID("i")),
+    ]),
+    ValInt(3)),
+  # PER: reassigning loop var in body doesn't prevent remaining iterations from running
+  # cnt increments once per iteration (all 3); C=100 doesn't replace next element assignment
+  ("DESIGNA cnt VT I\nPER i IN [I, II, III] FAC { DESIGNA i VT C\nDESIGNA cnt VT cnt + I }\ncnt",
+    Program([], [
+      Designa(ID("cnt"), Numeral("I")),
+      PerStatement(DataArray([Numeral("I"), Numeral("II"), Numeral("III")]), ID("i"), [
+        Designa(ID("i"), Numeral("C")),
+        Designa(ID("cnt"), BinOp(ID("cnt"), Numeral("I"), "SYMBOL_PLUS")),
+      ]),
+      ExpressionStatement(ID("cnt")),
+    ]),
+    ValInt(4)),
+  # PER: loop var after loop reflects the last body assignment, not the last array element
+  # body sets i=C=100 on every iteration; after loop ends, i stays at 100
+  ("PER i IN [I, II, III] FAC { DESIGNA i VT C }\ni",
+    Program([], [
+      PerStatement(DataArray([Numeral("I"), Numeral("II"), Numeral("III")]), ID("i"), [Designa(ID("i"), Numeral("C"))]),
+      ExpressionStatement(ID("i")),
+    ]),
+    ValInt(100)),
+  # DONICVM: counter holds last range value after loop ends
+  # [I VSQVE IV] = [1,2,3,4]; last value assigned by loop is IV=4
+  ("DONICVM i VT I VSQVE IV FAC { DESIGNA nop VT I }\ni",
+    Program([], [
+      PerStatement(DataRangeArray(Numeral("I"), Numeral("IV")), ID("i"), [Designa(ID("nop"), Numeral("I"))]),
+      ExpressionStatement(ID("i")),
+    ]),
+    ValInt(4)),
+  # DONICVM: reassigning counter inside body doesn't reduce the number of iterations
+  # range [I VSQVE IV] evaluated once; i reset each time; cnt still increments 4 times → 5
+  ("DESIGNA cnt VT I\nDONICVM i VT I VSQVE IV FAC { DESIGNA cnt VT cnt + I\nDESIGNA i VT C }\ncnt",
+    Program([], [
+      Designa(ID("cnt"), Numeral("I")),
+      PerStatement(DataRangeArray(Numeral("I"), Numeral("IV")), ID("i"), [
+        Designa(ID("cnt"), BinOp(ID("cnt"), Numeral("I"), "SYMBOL_PLUS")),
+        Designa(ID("i"), Numeral("C")),
+      ]),
+      ExpressionStatement(ID("cnt")),
+    ]),
+    ValInt(5)),
+  # DONICVM: ERVMPE exits loop early; counter persists at break value
+  ("DONICVM i VT I VSQVE X FAC {\nSI i EST III TVNC { ERVMPE }\n}\ni",
+    Program([], [
+      PerStatement(DataRangeArray(Numeral("I"), Numeral("X")), ID("i"), [
+        SiStatement(BinOp(ID("i"), Numeral("III"), "KEYWORD_EST"), [Erumpe()], None),
+      ]),
+      ExpressionStatement(ID("i")),
+    ]),
+    ValInt(3)),
+  # Function: modifying parameter inside function does not affect outer variable of same name
+  # outer n=1; f receives n=5 and modifies its local copy; outer n unchanged
+  ("DESIGNA n VT I\nDEFINI f (n) VT { DESIGNA n VT n + X\nREDI (n) }\nINVOCA f (V)\nn",
+    Program([], [
+      Designa(ID("n"), Numeral("I")),
+      Defini(ID("f"), [ID("n")], [Designa(ID("n"), BinOp(ID("n"), Numeral("X"), "SYMBOL_PLUS")), Redi([ID("n")])]),
+      ExpressionStatement(Invoca(ID("f"), [Numeral("V")])),
+      ExpressionStatement(ID("n")),
+    ]),
+    ValInt(1)),
+  # Function: mutating outer variable inside function (via DESIGNA) is not visible outside
+  # Invoca creates func_vtable = vtable.copy(); mutations to func_vtable don't propagate back
+  ("DESIGNA x VT I\nDEFINI f () VT { DESIGNA x VT C\nREDI (x) }\nINVOCA f ()\nx",
+    Program([], [
+      Designa(ID("x"), Numeral("I")),
+      Defini(ID("f"), [], [Designa(ID("x"), Numeral("C")), Redi([ID("x")])]),
+      ExpressionStatement(Invoca(ID("f"), [])),
+      ExpressionStatement(ID("x")),
+    ]),
+    ValInt(1)),
+  # Function: two successive calls with same parameter name don't share state
+  ("DEFINI f (n) VT { REDI (n * II) }\nINVOCA f (III) + INVOCA f (IV)",
+    Program([], [
+      Defini(ID("f"), [ID("n")], [Redi([BinOp(ID("n"), Numeral("II"), "SYMBOL_TIMES")])]),
+      ExpressionStatement(BinOp(Invoca(ID("f"), [Numeral("III")]), Invoca(ID("f"), [Numeral("IV")]), "SYMBOL_PLUS")),
+    ]),
+    ValInt(14)),
+  # Function: calling f(I) with param named n does not overwrite outer n=II
+  # f is defined before n is designated; INVOCA creates a local copy, outer vtable unchanged
+  ("DEFINI f (n) VT { REDI (n * II) }\nDESIGNA n VT II\nINVOCA f (I)\nn",
+    Program([], [
+      Defini(ID("f"), [ID("n")], [Redi([BinOp(ID("n"), Numeral("II"), "SYMBOL_TIMES")])]),
+      Designa(ID("n"), Numeral("II")),
+      ExpressionStatement(Invoca(ID("f"), [Numeral("I")])),
+      ExpressionStatement(ID("n")),
+    ]),
+    ValInt(2)),
+]
+
+class TestScope(unittest.TestCase):
+  @parameterized.expand(scope_tests)
+  def test_scope(self, source, nodes, value):
+    run_test(self, source, nodes, value)
+
+# --- First-class functions / FVNCTIO ---
+
+fvnctio_tests = [
+  # Lambda assigned to variable, then called
+  (
+    "DESIGNA f VT FVNCTIO (x) VT { REDI (x + I) }\nINVOCA f (V)",
+    Program([], [
+      Designa(ID("f"), Fvnctio([ID("x")], [Redi([BinOp(ID("x"), Numeral("I"), "SYMBOL_PLUS")])])),
+      ExpressionStatement(Invoca(ID("f"), [Numeral("V")])),
+    ]),
+    ValInt(6),
+  ),
+  # IIFE: immediately invoked lambda
+  (
+    "INVOCA FVNCTIO (x) VT { REDI (x * II) } (III)",
+    Program([], [
+      ExpressionStatement(Invoca(
+        Fvnctio([ID("x")], [Redi([BinOp(ID("x"), Numeral("II"), "SYMBOL_TIMES")])]),
+        [Numeral("III")],
+      )),
+    ]),
+    ValInt(6),
+  ),
+  # Zero-arg lambda
+  (
+    "INVOCA FVNCTIO () VT { REDI (XLII) } ()",
+    Program([], [
+      ExpressionStatement(Invoca(
+        Fvnctio([], [Redi([Numeral("XLII")])]),
+        [],
+      )),
+    ]),
+    ValInt(42),
+  ),
+  # Function passed as argument
+  (
+    "DEFINI apply (f, x) VT { REDI (INVOCA f (x)) }\n"
+    "DESIGNA dbl VT FVNCTIO (n) VT { REDI (n * II) }\n"
+    "INVOCA apply (dbl, V)",
+    Program([], [
+      Defini(ID("apply"), [ID("f"), ID("x")], [
+        Redi([Invoca(ID("f"), [ID("x")])])
+      ]),
+      Designa(ID("dbl"), Fvnctio([ID("n")], [
+        Redi([BinOp(ID("n"), Numeral("II"), "SYMBOL_TIMES")])
+      ])),
+      ExpressionStatement(Invoca(ID("apply"), [ID("dbl"), Numeral("V")])),
+    ]),
+    ValInt(10),
+  ),
+  # Lambda uses caller-scope variable (copy-caller semantics)
+  (
+    "DESIGNA n VT III\n"
+    "DESIGNA f VT FVNCTIO (x) VT { REDI (x + n) }\n"
+    "INVOCA f (V)",
+    Program([], [
+      Designa(ID("n"), Numeral("III")),
+      Designa(ID("f"), Fvnctio([ID("x")], [
+        Redi([BinOp(ID("x"), ID("n"), "SYMBOL_PLUS")])
+      ])),
+      ExpressionStatement(Invoca(ID("f"), [Numeral("V")])),
+    ]),
+    ValInt(8),
+  ),
+  # Named function passed as value
+  (
+    "DEFINI sqr (x) VT { REDI (x * x) }\n"
+    "DESIGNA f VT sqr\n"
+    "INVOCA f (IV)",
+    Program([], [
+      Defini(ID("sqr"), [ID("x")], [Redi([BinOp(ID("x"), ID("x"), "SYMBOL_TIMES")])]),
+      Designa(ID("f"), ID("sqr")),
+      ExpressionStatement(Invoca(ID("f"), [Numeral("IV")])),
+    ]),
+    ValInt(16),
+  ),
+  # Nested lambdas
+  (
+    "INVOCA FVNCTIO (x) VT { REDI (INVOCA FVNCTIO (y) VT { REDI (y + I) } (x)) } (V)",
+    Program([], [
+      ExpressionStatement(Invoca(
+        Fvnctio([ID("x")], [
+          Redi([Invoca(
+            Fvnctio([ID("y")], [Redi([BinOp(ID("y"), Numeral("I"), "SYMBOL_PLUS")])]),
+            [ID("x")],
+          )])
+        ]),
+        [Numeral("V")],
+      )),
+    ]),
+    ValInt(6),
+  ),
+  # DIC on a function value
+  (
+    "DESIGNA f VT FVNCTIO (x) VT { REDI (x) }\nDIC(f)",
+    Program([], [
+      Designa(ID("f"), Fvnctio([ID("x")], [Redi([ID("x")])])),
+      ExpressionStatement(BuiltIn("DIC", [ID("f")])),
+    ]),
+    ValStr("FVNCTIO"),
+    "FVNCTIO\n",
+  ),
+  # Lambda stored in array, called via index
+  (
+    "DESIGNA fns VT [FVNCTIO (x) VT { REDI (x + I) }, FVNCTIO (x) VT { REDI (x * II) }]\n"
+    "INVOCA fns[I] (V)",
+    Program([], [
+      Designa(ID("fns"), DataArray([
+        Fvnctio([ID("x")], [Redi([BinOp(ID("x"), Numeral("I"), "SYMBOL_PLUS")])]),
+        Fvnctio([ID("x")], [Redi([BinOp(ID("x"), Numeral("II"), "SYMBOL_TIMES")])]),
+      ])),
+      ExpressionStatement(Invoca(
+        ArrayIndex(ID("fns"), Numeral("I")),
+        [Numeral("V")],
+      )),
+    ]),
+    ValInt(6),
+  ),
+  # Lambda stored in dict, called via key
+  (
+    'DESIGNA d VT TABVLA {"add" VT FVNCTIO (x) VT { REDI (x + I) }}\n'
+    'INVOCA d["add"] (V)',
+    Program([], [
+      Designa(ID("d"), DataDict([
+        (String("add"), Fvnctio([ID("x")], [Redi([BinOp(ID("x"), Numeral("I"), "SYMBOL_PLUS")])])),
+      ])),
+      ExpressionStatement(Invoca(
+        ArrayIndex(ID("d"), String("add")),
+        [Numeral("V")],
+      )),
+    ]),
+    ValInt(6),
+  ),
+  # Multi-param lambda
+  (
+    "DESIGNA add VT FVNCTIO (a, b) VT { REDI (a + b) }\nINVOCA add (III, IV)",
+    Program([], [
+      Designa(ID("add"), Fvnctio([ID("a"), ID("b")], [
+        Redi([BinOp(ID("a"), ID("b"), "SYMBOL_PLUS")])
+      ])),
+      ExpressionStatement(Invoca(ID("add"), [Numeral("III"), Numeral("IV")])),
+    ]),
+    ValInt(7),
+  ),
+]
+
+class TestFvnctio(unittest.TestCase):
+  @parameterized.expand(fvnctio_tests)
+  def test_fvnctio(self, source, nodes, value, output=""):
+    run_test(self, source, nodes, value, output)
+
+# --- Tempta/Cape (try/catch) ---
+
+tempta_tests = [
+  # Try block succeeds — catch not entered
+  (
+    "TEMPTA {\nDESIGNA r VT I\n} CAPE e {\nDESIGNA r VT II\n}\nr",
+    Program([], [
+      TemptaStatement(
+        [Designa(ID("r"), Numeral("I"))],
+        ID("e"),
+        [Designa(ID("r"), Numeral("II"))],
+      ),
+      ExpressionStatement(ID("r")),
+    ]),
+    ValInt(1),
+  ),
+  # Try block errors — caught by catch
+  (
+    "TEMPTA {\nDESIGNA r VT I / NVLLVS\n} CAPE e {\nDESIGNA r VT II\n}\nr",
+    Program([], [
+      TemptaStatement(
+        [Designa(ID("r"), BinOp(Numeral("I"), Nullus(), "SYMBOL_DIVIDE"))],
+        ID("e"),
+        [Designa(ID("r"), Numeral("II"))],
+      ),
+      ExpressionStatement(ID("r")),
+    ]),
+    ValInt(2),
+  ),
+  # Error variable contains the error message
+  (
+    'DESIGNA e VT NVLLVS\nTEMPTA {\nDESIGNA r VT I / NVLLVS\n} CAPE e {\nNVLLVS\n}\ne',
+    Program([], [
+      Designa(ID("e"), Nullus()),
+      TemptaStatement(
+        [Designa(ID("r"), BinOp(Numeral("I"), Nullus(), "SYMBOL_DIVIDE"))],
+        ID("e"),
+        [ExpressionStatement(Nullus())],
+      ),
+      ExpressionStatement(ID("e")),
+    ]),
+    ValStr("Division by zero"),
+  ),
+  # Nested tempta — inner catches, outer unaffected
+  (
+    "DESIGNA r VT NVLLVS\nTEMPTA {\nTEMPTA {\nDESIGNA r VT I / NVLLVS\n} CAPE e {\nDESIGNA r VT I\n}\n} CAPE e {\nDESIGNA r VT II\n}\nr",
+    Program([], [
+      Designa(ID("r"), Nullus()),
+      TemptaStatement(
+        [TemptaStatement(
+          [Designa(ID("r"), BinOp(Numeral("I"), Nullus(), "SYMBOL_DIVIDE"))],
+          ID("e"),
+          [Designa(ID("r"), Numeral("I"))],
+        )],
+        ID("e"),
+        [Designa(ID("r"), Numeral("II"))],
+      ),
+      ExpressionStatement(ID("r")),
+    ]),
+    ValInt(1),
+  ),
+  # REDI inside catch block
+  (
+    "DEFINI f () VT {\nTEMPTA {\nDESIGNA x VT I / NVLLVS\n} CAPE e {\nREDI (III)\n}\nREDI (IV)\n}\nINVOCA f ()",
+    Program([], [
+      Defini(ID("f"), [], [
+        TemptaStatement(
+          [Designa(ID("x"), BinOp(Numeral("I"), Nullus(), "SYMBOL_DIVIDE"))],
+          ID("e"),
+          [Redi([Numeral("III")])],
+        ),
+        Redi([Numeral("IV")]),
+      ]),
+      ExpressionStatement(Invoca(ID("f"), [])),
+    ]),
+    ValInt(3),
+  ),
+  # ERVMPE inside catch block (inside a loop)
+  (
+    "DESIGNA r VT NVLLVS\nDVM r EST I FAC {\nTEMPTA {\nDESIGNA x VT I / NVLLVS\n} CAPE e {\nDESIGNA r VT I\nERVMPE\n}\n}\nr",
+    Program([], [
+      Designa(ID("r"), Nullus()),
+      DumStatement(
+        BinOp(ID("r"), Numeral("I"), "KEYWORD_EST"),
+        [TemptaStatement(
+          [Designa(ID("x"), BinOp(Numeral("I"), Nullus(), "SYMBOL_DIVIDE"))],
+          ID("e"),
+          [Designa(ID("r"), Numeral("I")), Erumpe()],
+        )],
+      ),
+      ExpressionStatement(ID("r")),
+    ]),
+    ValInt(1),
+  ),
+  # Statement after error in try block is not executed
+  (
+    "DESIGNA r VT NVLLVS\nTEMPTA {\nDESIGNA x VT I / NVLLVS\nDESIGNA r VT III\n} CAPE e {\nDESIGNA r VT II\n}\nr",
+    Program([], [
+      Designa(ID("r"), Nullus()),
+      TemptaStatement(
+        [Designa(ID("x"), BinOp(Numeral("I"), Nullus(), "SYMBOL_DIVIDE")),
+         Designa(ID("r"), Numeral("III"))],
+        ID("e"),
+        [Designa(ID("r"), Numeral("II"))],
+      ),
+      ExpressionStatement(ID("r")),
+    ]),
+    ValInt(2),
+  ),
+]
+
+class TestTempta(unittest.TestCase):
+  @parameterized.expand(tempta_tests)
+  def test_tempta(self, source, nodes, value, output=""):
+    run_test(self, source, nodes, value, output)

tests/12_test_failures.py

@@ -0,0 +1,148 @@
+from tests._helpers import (
+  unittest, parameterized, Fraction, time,
+  run_test, run_compiler_error_test,
+  ArrayIndex, ArraySlice, Bool, BinOp, BuiltIn, DataArray, DataDict, DataRangeArray,
+  Defini, Continva, Designa, DesignaDestructure, DesignaIndex, DumStatement,
+  Erumpe, ExpressionStatement, Fvnctio, ID, InterpolatedString, Invoca,
+  ModuleCall, Nullus, Numeral, PerStatement, Program, Redi, SiStatement,
+  String, TemptaStatement, UnaryMinus, UnaryNot, Fractio, frac_to_fraction,
+  fraction_to_frac, num_to_int, int_to_num, make_string,
+  ValInt, ValStr, ValBool, ValList, ValDict, ValNul, ValFunc, ValFrac,
+  CentvrionError, _RUNTIME_C, _cent_rng,
+  Lexer, Parser, compile_program,
+  os, subprocess, tempfile, StringIO, patch,
+)
+
+
+# --- Errors ---
+
+error_tests = [
+  ("x", CentvrionError),                                    # undefined variable
+  ("INVOCA f ()", CentvrionError),                          # undefined function
+  ("DESIGNA VT III", SyntaxError),                          # parse error: missing id after DESIGNA
+  ("DESIGNA x III", SyntaxError),                           # parse error: missing VT
+  ("DEFINI f () VT { REDI(I) }\nf()", SyntaxError),        # function call without INVOCA (no args)
+  ("DEFINI f (x) VT { REDI(x) }\nf(I)", SyntaxError),     # function call without INVOCA (with args)
+  ("DIC(M + M + M + M)", CentvrionError),                  # output > 3999 without MAGNVM
+  ("IIII", CentvrionError),                                 # invalid Roman numeral in source
+  ("FORTVITVS_NVMERVS(I, X)", CentvrionError),                 # requires FORS module
+  ('NVMERVS(I)', CentvrionError),                              # NVMERVS expects a string, not int
+  ('NVMERVS("ABC")', CentvrionError),                          # invalid Roman numeral string
+  ('NVMERVS("XIV", "IX")', CentvrionError),                    # too many args
+  ("DEFINI f (x) VT { REDI(x) }\nINVOCA f (I, II)", CentvrionError),  # too many args
+  ("DEFINI f (x, y) VT { REDI(x) }\nINVOCA f (I)", CentvrionError),   # too few args
+  ("DEFINI f () VT { REDI(I) }\nINVOCA f (I)", CentvrionError),        # args to zero-param function
+  ("SI NVLLVS TVNC { DESIGNA r VT I }", CentvrionError),               # NVLLVS cannot be used as boolean
+  ("NVLLVS AVT VERITAS", CentvrionError),                              # NVLLVS cannot be used as boolean in AVT
+  ("FALSITAS AVT NVLLVS", CentvrionError),                             # no short-circuit: right side evaluated, NVLLVS not boolean
+  ("VERITAS ET NVLLVS", CentvrionError),                               # no short-circuit: right side evaluated, NVLLVS not boolean
+  ("NVLLVS ET VERITAS", CentvrionError),                               # NVLLVS cannot be used as boolean in ET
+  ('I @ [II]', CentvrionError),                                         # @ requires two arrays (int @ array)
+  ('[I] @ "hello"', CentvrionError),                                    # @ requires two arrays (array @ string)
+  ('"a" @ "b"', CentvrionError),                                        # @ requires two arrays (string @ string)
+  ('"hello" + " world"', CentvrionError),                              # use & for string concatenation, not +
+  ("[I, II][III]", CentvrionError),                                    # index too high
+  ("CVM SVBNVLLA\n[I, II][-I]", CentvrionError),                       # negative index
+  ("[I, II][-I]", CentvrionError),                                     # negative value
+  ("I / NVLLVS", CentvrionError),                                      # division by zero (NVLLVS coerces to 0)
+  ("V RELIQVVM NVLLVS", CentvrionError),                               # modulo by zero (NVLLVS coerces to 0)
+  ("NVLLVS RELIQVVM NVLLVS", CentvrionError),                          # modulo by zero (both NVLLVS)
+  ("I / [I, II]", CentvrionError),                                     # division with array operand
+  ("I - \"hello\"", CentvrionError),                                   # subtraction with string
+  ("I * \"hello\"", CentvrionError),                                   # multiplication with string
+  ("\"hello\" MINVS \"world\"", CentvrionError),                       # comparison with strings
+  ('"a" HAVD_PLVS "b"', CentvrionError),                               # HAVD_PLVS on strings
+  ('[I] HAVD_MINVS [II]', CentvrionError),                             # HAVD_MINVS on arrays
+  ("I[I]", CentvrionError),                                           # indexing a non-array
+  ('"SALVTE"[VII]', CentvrionError),                                   # string index out of range
+  ('"SALVTE"[NVLLVS]', CentvrionError),                                # string index with non-integer
+  ('"SALVTE"[II VSQVE VII]', CentvrionError),                          # string slice out of range
+  ('"SALVTE"[III VSQVE II]', CentvrionError),                          # string slice from > to
+  ("DESIGNA x VT I\nDESIGNA x[I] VT II", CentvrionError),             # index-assign to non-array
+  ("SEMEN(I)", CentvrionError),                                        # requires FORS module
+  ('CVM FORS\nSEMEN("abc")', CentvrionError),                          # SEMEN requires integer seed
+  ("FORTVITA_ELECTIO([])", CentvrionError),                           # FORS required for FORTVITA_ELECTIO
+  ("CVM FORS\nFORTVITA_ELECTIO([])", CentvrionError),                 # FORTVITA_ELECTIO on empty array
+  ("CVM FORS\nFORTVITVS_NVMERVS(X, I)", CentvrionError),                  # FORTVITVS_NVMERVS a > b
+  ("PER i IN I FAC { DIC(i) }", CentvrionError),                     # PER over non-array
+  ("DECIMATIO([I, II, III])", CentvrionError),                          # FORS required for DECIMATIO
+  ("CVM FORS\nDECIMATIO(I)", CentvrionError),                          # DECIMATIO requires an array
+  ("LONGITVDO(I)", CentvrionError),                                    # LONGITVDO on non-array
+  ("ORDINA(I)", CentvrionError),                                       # ORDINA on non-array
+  ('ORDINA([I, "a"])', CentvrionError),                                # ORDINA mixed types
+  ("DESIGNA x VT I\nORDINA(x)", CentvrionError),                       # ORDINA on id (non-array)
+  ("SENATVS(I)", CentvrionError),                                      # SENATVS requires booleans
+  ("SENATVS(VERITAS, I)", CentvrionError),                             # SENATVS mixed types
+  ("SENATVS([I, II, III])", CentvrionError),                           # SENATVS array of non-bools
+  ('LEGE("x.txt")', CentvrionError),                                    # SCRIPTA required for LEGE
+  ('SCRIBE("x.txt", "hi")', CentvrionError),                            # SCRIPTA required for SCRIBE
+  ('ADIVNGE("x.txt", "hi")', CentvrionError),                           # SCRIPTA required for ADIVNGE
+  ("DESIGNA x VT I\nINVOCA x ()", CentvrionError),                     # invoking a non-function
+  ("SI I TVNC { DESIGNA r VT I }", CentvrionError),                    # non-bool SI condition: int
+  ("IIIS", CentvrionError),                                            # fraction without FRACTIO module
+  ("CVM FRACTIO\n[I, II, III][IIIS]", CentvrionError),                 # fractional index (IIIS = 7/2)
+  ("CVM FRACTIO\n[I, II, III][I / II]", CentvrionError),               # fractional index from division (1/2)
+  ("DESIGNA z VT I - I\nSI z TVNC { DESIGNA r VT I }", CentvrionError), # non-bool SI condition: zero int
+  ("SI [I] TVNC { DESIGNA r VT I }", CentvrionError),                  # non-bool SI condition: non-empty list
+  ("SI [] TVNC { DESIGNA r VT I }", CentvrionError),                   # non-bool SI condition: empty list
+  ("DESIGNA x VT I\nDVM x FAC {\nDESIGNA x VT x + I\n}", CentvrionError),  # non-bool DVM condition: int
+  ("NON I", CentvrionError),                                               # NON on integer
+  ("DESIGNA z VT I - I\nNON z", CentvrionError),                          # NON on zero integer
+  ('NON "hello"', CentvrionError),                                         # NON on string
+  ("DESIGNA a, b VT III", CentvrionError),                                 # destructure non-array
+  ("DESIGNA a, b VT [I]", CentvrionError),                                # destructure length mismatch: too many targets
+  ("DESIGNA a, b VT [I, II, III]", CentvrionError),                       # destructure length mismatch: too few targets
+  ("PER a, b IN [I, II, III] FAC { DIC(a) }", CentvrionError),           # PER destructure: element is not an array
+  ("PER a, b IN [[I], [II]] FAC { DIC(a) }", CentvrionError),            # PER destructure: wrong number of elements
+  ("[I, II, III][II VSQVE IV]", CentvrionError),                           # slice upper bound out of range
+  ("[I, II, III][NVLLVS VSQVE II]", CentvrionError),                      # slice with non-integer bound
+  ("I[I VSQVE II]", CentvrionError),                                      # slice on non-array
+  ("[I, II, III][III VSQVE I]", CentvrionError),                           # slice from > to
+  ("CVM SVBNVLLA\n[I, II, III][-I VSQVE II]", CentvrionError),            # slice with negative lower bound
+  ("CVM SVBNVLLA\n[I, II, III][I VSQVE -I]", CentvrionError),             # slice with negative upper bound
+  ("CVM FRACTIO\n[I, II, III][IIIS VSQVE III]", CentvrionError),          # slice with fractional lower bound
+  ("CVM FRACTIO\n[I, II, III][I VSQVE IIIS]", CentvrionError),            # slice with fractional upper bound
+  ("CVM FRACTIO\n[I, II, III][I / II VSQVE III]", CentvrionError),        # slice with division-fraction lower bound
+  ("TEMPTA {\nDESIGNA x VT I / NVLLVS\n} CAPE e {\nDESIGNA y VT I / NVLLVS\n}", CentvrionError),  # uncaught error in catch block propagates
+  ('QVAERE(I, "abc")', CentvrionError),                                     # QVAERE requires strings, not int
+  ('QVAERE("abc", I)', CentvrionError),                                     # QVAERE requires strings, not int
+  ('QVAERE("[", "abc")', CentvrionError),                                   # QVAERE invalid regex
+  ('SVBSTITVE(I, "b", "c")', CentvrionError),                                # SVBSTITVE requires strings, not int pattern
+  ('SVBSTITVE("a", I, "c")', CentvrionError),                                # SVBSTITVE requires strings, not int replacement
+  ('SVBSTITVE("a", "b", I)', CentvrionError),                                # SVBSTITVE requires strings, not int text
+  ('SVBSTITVE("[", "b", "c")', CentvrionError),                              # SVBSTITVE invalid regex
+  ("SVBSTITVE('(a)', '\\1', 'a')", CentvrionError),                          # Arabic backref in replacement
+  ("QVAERE('(.)\\1', 'aa')", CentvrionError),                               # Arabic backref in pattern
+  ("QVAERE('a{3}', 'aaa')", CentvrionError),                                # Arabic quantifier in pattern
+  ('SCINDE(I, ",")', CentvrionError),                                         # SCINDE requires strings, not int
+  ('SCINDE("a", I)', CentvrionError),                                         # SCINDE requires strings, not int delimiter
+  ('MAIVSCVLA(I)', CentvrionError),                                           # MAIVSCVLA requires a string, not int
+  ('MAIVSCVLA()', CentvrionError),                                            # MAIVSCVLA requires exactly 1 arg
+  ('MAIVSCVLA("a", "b")', CentvrionError),                                    # MAIVSCVLA too many args
+  ('MINVSCVLA(I)', CentvrionError),                                           # MINVSCVLA requires a string, not int
+  ('MINVSCVLA()', CentvrionError),                                            # MINVSCVLA requires exactly 1 arg
+  ('MINVSCVLA("a", "b")', CentvrionError),                                    # MINVSCVLA too many args
+  ('PETE("http://example.com")', CentvrionError),                             # RETE required for PETE
+  ('CVM RETE\nPETE(I)', CentvrionError),                                      # PETE requires a string URL
+  ('PETITVR("/", FVNCTIO (r) VT {\nREDI("hi")\n})', CentvrionError),           # RETE required for PETITVR
+  ('CVM RETE\nPETITVR(I, FVNCTIO (r) VT {\nREDI("hi")\n})', CentvrionError), # PETITVR path must be string
+  ('CVM RETE\nPETITVR("/", "not a func")', CentvrionError),                   # PETITVR handler must be function
+  ('CVM RETE\nAVSCVLTA(LXXX)', CentvrionError),                               # AVSCVLTA: no routes registered
+  ('AVSCVLTA(LXXX)', CentvrionError),                                         # RETE required for AVSCVLTA
+  ('CVM RETE\nPETITVR("/", FVNCTIO (r) VT {\nREDI("hi")\n})\nAVSCVLTA("text")', CentvrionError),  # AVSCVLTA port must be integer
+  ("DONICVM i VT I VSQVE X GRADV I - I FAC { DIC(i) }", CentvrionError),  # GRADV zero step
+  ('DONICVM i VT I VSQVE X GRADV "foo" FAC { DIC(i) }', CentvrionError),  # GRADV non-integer step
+]
+
+class TestErrors(unittest.TestCase):
+  @parameterized.expand(error_tests)
+  def test_errors(self, source, error_type):
+    with self.assertRaises(error_type):
+      run_test(self, source, None, None)
+
+compiler_error_tests = [(s, e) for s, e in error_tests if e == CentvrionError]
+
+class TestCompilerErrors(unittest.TestCase):
+  @parameterized.expand(compiler_error_tests)
+  def test_compiler_errors(self, source, error_type):
+    run_compiler_error_test(self, source)

tests/_helpers.py

@@ -0,0 +1,135 @@
+import os
+import subprocess
+import tempfile
+import time
+import unittest
+from io import StringIO
+from unittest.mock import patch
+from parameterized import parameterized
+
+from fractions import Fraction
+
+from centvrion.ast_nodes import (
+  ArrayIndex, ArraySlice, Bool, BinOp, BuiltIn, DataArray, DataDict, DataRangeArray,
+  Defini, Continva, Designa, DesignaDestructure, DesignaIndex, DumStatement,
+  Erumpe, ExpressionStatement, Fvnctio, ID, InterpolatedString, Invoca,
+  ModuleCall, Nullus, Numeral, PerStatement, Program, Redi, SiStatement,
+  String, TemptaStatement, UnaryMinus, UnaryNot, Fractio, frac_to_fraction,
+  fraction_to_frac, num_to_int, int_to_num, make_string,
+  _cent_rng,
+)
+from centvrion.compiler.emitter import compile_program
+from centvrion.errors import CentvrionError
+from centvrion.lexer import Lexer
+from centvrion.parser import Parser
+from centvrion.values import ValInt, ValStr, ValBool, ValList, ValDict, ValNul, ValFunc, ValFrac
+
+_RUNTIME_C = os.path.join(
+  os.path.dirname(__file__), "..",
+  "centvrion", "compiler", "runtime", "cent_runtime.c"
+)
+
+def run_test(self, source, target_nodes, target_value, target_output="", input_lines=[]):
+  _cent_rng.seed(1)
+
+  lexer = Lexer().get_lexer()
+  tokens = lexer.lex(source + "\n")
+  program = Parser().parse(tokens)
+
+  ##########################
+  ####### Parser Test ######
+  ##########################
+  if target_nodes is not None:
+    self.assertEqual(
+      program,
+      target_nodes,
+      f"Parser test:\n{program}\n{target_nodes}"
+    )
+
+  ##########################
+  #### Interpreter Test ####
+  ##########################
+  captured = StringIO()
+  try:
+    if input_lines:
+      inputs = iter(input_lines)
+      with patch("builtins.input", lambda: next(inputs)), patch("sys.stdout", captured):
+        result = program.eval()
+    else:
+      with patch("sys.stdout", captured):
+        result = program.eval()
+  except Exception as e:
+    raise e
+
+  self.assertEqual(result, target_value, "Return value test")
+  self.assertEqual(captured.getvalue(), target_output, "Output test")
+
+  ##########################
+  ###### Printer Test ######
+  ##########################
+  try:
+    new_text = program.print()
+    new_tokens = Lexer().get_lexer().lex(new_text + "\n")
+    new_nodes = Parser().parse(new_tokens)
+  except Exception as e:
+    raise Exception(f"###Printer test###\n{new_text}") from e
+  self.assertEqual(
+    program,
+    new_nodes,
+    f"Printer test\n{source}\n{new_text}"
+  )
+
+  ##########################
+  ###### Compiler Test #####
+  ##########################
+  c_source = compile_program(program)
+  # Force deterministic RNG seed=1 for test reproducibility
+  c_source = c_source.replace("cent_init();", "cent_init(); cent_semen((CentValue){.type=CENT_INT, .ival=1});", 1)
+  with tempfile.NamedTemporaryFile(suffix=".c", delete=False, mode="w") as tmp_c:
+    tmp_c.write(c_source)
+    tmp_c_path = tmp_c.name
+  with tempfile.NamedTemporaryFile(suffix="", delete=False) as tmp_bin:
+    tmp_bin_path = tmp_bin.name
+  try:
+    subprocess.run(
+      ["gcc", "-O2", tmp_c_path, _RUNTIME_C, "-o", tmp_bin_path, "-lcurl", "-lmicrohttpd"],
+      check=True, capture_output=True,
+    )
+    stdin_data = "".join(f"{l}\n" for l in input_lines)
+    proc = subprocess.run(
+      [tmp_bin_path],
+      input=stdin_data, capture_output=True, text=True,
+    )
+    self.assertEqual(proc.returncode, 0, f"Compiler binary exited non-zero:\n{proc.stderr}")
+    self.assertEqual(proc.stdout, target_output, "Compiler output test")
+  finally:
+    os.unlink(tmp_c_path)
+    os.unlink(tmp_bin_path)
+
+  assert target_nodes is not None, "All tests must have target nodes"
+
+
+def run_compiler_error_test(self, source):
+  lexer = Lexer().get_lexer()
+  tokens = lexer.lex(source + "\n")
+  program = Parser().parse(tokens)
+  try:
+    c_source = compile_program(program)
+  except CentvrionError:
+    return  # compile-time detection is valid
+  with tempfile.NamedTemporaryFile(suffix=".c", delete=False, mode="w") as tmp_c:
+    tmp_c.write(c_source)
+    tmp_c_path = tmp_c.name
+  with tempfile.NamedTemporaryFile(suffix="", delete=False) as tmp_bin:
+    tmp_bin_path = tmp_bin.name
+  try:
+    subprocess.run(
+      ["gcc", "-O2", tmp_c_path, _RUNTIME_C, "-o", tmp_bin_path, "-lcurl", "-lmicrohttpd"],
+      check=True, capture_output=True,
+    )
+    proc = subprocess.run([tmp_bin_path], capture_output=True, text=True)
+    self.assertNotEqual(proc.returncode, 0, "Expected non-zero exit for error program")
+    self.assertTrue(proc.stderr.strip(), "Expected error message on stderr")
+  finally:
+    os.unlink(tmp_c_path)
+    os.unlink(tmp_bin_path)

vscode-extension/package.json

@@ -20,6 +20,10 @@
             "language": "cent",
             "scopeName": "source.cent",
             "path": "./syntaxes/cent.tmLanguage.json"
+        }],
+        "snippets": [{
+            "language": "cent",
+            "path": "./snippets/cent.json"
         }]
     }
 }

vscode-extension/snippets/cent.json

@@ -0,0 +1,98 @@
+{
+  "SI": {
+    "prefix": "SI",
+    "body": ["SI ${1:condicio} TVNC {", "  $0", "}"],
+    "description": "if/then conditional"
+  },
+  "DVM": {
+    "prefix": "DVM",
+    "body": ["DVM ${1:condicio} FAC {", "  $0", "}"],
+    "description": "while loop"
+  },
+  "PER": {
+    "prefix": "PER",
+    "body": ["PER ${1:elementum} IN ${2:tabula} FAC {", "  $0", "}"],
+    "description": "for-each loop"
+  },
+  "DEFINI": {
+    "prefix": "DEFINI",
+    "body": ["DEFINI ${1:nomen} ${2:parametri} VT {", "  $0", "}"],
+    "description": "define named function"
+  },
+  "DONICVM": {
+    "prefix": "DONICVM",
+    "body": ["DONICVM ${1:i} VT ${2:I} VSQVE ${3:X} FAC {", "  $0", "}"],
+    "description": "numeric range loop"
+  },
+
+  "AETERNVM": { "prefix": "AETERNVM", "body": "AETERNVM", "description": "infinite loop" },
+  "ALIVD": { "prefix": "ALIVD", "body": "ALIVD", "description": "else / else-if branch" },
+  "AVGE": { "prefix": "AVGE", "body": "AVGE", "description": "compound addition assignment (+=)" },
+  "AVT": { "prefix": "AVT", "body": "AVT", "description": "logical or" },
+  "CAPE": { "prefix": "CAPE", "body": "CAPE", "description": "catch block header" },
+  "CONTINVA": { "prefix": "CONTINVA", "body": "CONTINVA", "description": "skip to next loop iteration" },
+  "CVM": { "prefix": "CVM", "body": "CVM", "description": "include module" },
+  "DESIGNA": { "prefix": "DESIGNA", "body": "DESIGNA", "description": "declare and assign a variable" },
+  "DISPAR": { "prefix": "DISPAR", "body": "DISPAR", "description": "not-equal comparison (!=)" },
+  "DIVIDE": { "prefix": "DIVIDE", "body": "DIVIDE", "description": "compound division assignment (/=)" },
+  "ERVMPE": { "prefix": "ERVMPE", "body": "ERVMPE", "description": "break out of loop" },
+  "EST": { "prefix": "EST", "body": "EST", "description": "equality comparison (==)" },
+  "ET": { "prefix": "ET", "body": "ET", "description": "logical and" },
+  "FAC": { "prefix": "FAC", "body": "FAC", "description": "block opener for loops and functions" },
+  "FALSITAS": { "prefix": "FALSITAS", "body": "FALSITAS", "description": "boolean false" },
+  "FVNCTIO": { "prefix": "FVNCTIO", "body": "FVNCTIO", "description": "anonymous function expression" },
+  "GRADV": { "prefix": "GRADV", "body": "GRADV", "description": "DONICVM range step (by a step of)" },
+  "HAVD_MINVS": { "prefix": "HAVD_MINVS", "body": "HAVD_MINVS", "description": "greater-or-equal (>=)" },
+  "HAVD_PLVS": { "prefix": "HAVD_PLVS", "body": "HAVD_PLVS", "description": "less-or-equal (<=)" },
+  "IN": { "prefix": "IN", "body": "IN", "description": "PER-loop iterator separator" },
+  "INVOCA": { "prefix": "INVOCA", "body": "INVOCA", "description": "invoke / call a function" },
+  "MINVE": { "prefix": "MINVE", "body": "MINVE", "description": "compound subtraction assignment (-=)" },
+  "MINVS": { "prefix": "MINVS", "body": "MINVS", "description": "less-than comparison (<)" },
+  "MVLTIPLICA": { "prefix": "MVLTIPLICA", "body": "MVLTIPLICA", "description": "compound multiplication assignment (*=)" },
+  "NON": { "prefix": "NON", "body": "NON", "description": "logical not" },
+  "NVLLVS": { "prefix": "NVLLVS", "body": "NVLLVS", "description": "null value" },
+  "PLVS": { "prefix": "PLVS", "body": "PLVS", "description": "greater-than comparison (>)" },
+  "REDI": { "prefix": "REDI", "body": "REDI", "description": "return from function" },
+  "RELIQVVM": { "prefix": "RELIQVVM", "body": "RELIQVVM", "description": "modulo / remainder" },
+  "TABVLA": { "prefix": "TABVLA", "body": "TABVLA", "description": "dict literal opener" },
+  "TEMPTA": { "prefix": "TEMPTA", "body": "TEMPTA", "description": "try block header" },
+  "TVNC": { "prefix": "TVNC", "body": "TVNC", "description": "then (SI branch)" },
+  "VERITAS": { "prefix": "VERITAS", "body": "VERITAS", "description": "boolean true" },
+  "VSQVE": { "prefix": "VSQVE", "body": "VSQVE", "description": "upper bound of DONICVM range" },
+  "VT": { "prefix": "VT", "body": "VT", "description": "assignment / binding connective" },
+
+  "ADIVNGE": { "prefix": "ADIVNGE", "body": "ADIVNGE", "description": "append string to file (SCRIPTA module)" },
+  "AVDI": { "prefix": "AVDI", "body": "AVDI", "description": "read a line from stdin" },
+  "AVDI_NVMERVS": { "prefix": "AVDI_NVMERVS", "body": "AVDI_NVMERVS", "description": "read a Roman numeral from stdin" },
+  "AVSCVLTA": { "prefix": "AVSCVLTA", "body": "AVSCVLTA", "description": "start HTTP server on port (RETE module)" },
+  "CLAVES": { "prefix": "CLAVES", "body": "CLAVES", "description": "return the keys of a dict" },
+  "DECIMATIO": { "prefix": "DECIMATIO", "body": "DECIMATIO", "description": "remove a random tenth of an array (FORS module)" },
+  "DIC": { "prefix": "DIC", "body": "DIC", "description": "print value(s) to stdout" },
+  "DORMI": { "prefix": "DORMI", "body": "DORMI", "description": "sleep for N seconds" },
+  "EVERRE": { "prefix": "EVERRE", "body": "EVERRE", "description": "clear the terminal screen" },
+  "FORTVITA_ELECTIO": { "prefix": "FORTVITA_ELECTIO", "body": "FORTVITA_ELECTIO", "description": "pick a random element from an array (FORS module)" },
+  "FORTVITVS_NVMERVS": { "prefix": "FORTVITVS_NVMERVS", "body": "FORTVITVS_NVMERVS", "description": "random integer in a range (FORS module)" },
+  "LEGE": { "prefix": "LEGE", "body": "LEGE", "description": "read file contents (SCRIPTA module)" },
+  "LITTERA": { "prefix": "LITTERA", "body": "LITTERA", "description": "coerce any value to its display string" },
+  "LONGITVDO": { "prefix": "LONGITVDO", "body": "LONGITVDO", "description": "length of array, string, or dict" },
+  "MAIVSCVLA": { "prefix": "MAIVSCVLA", "body": "MAIVSCVLA", "description": "uppercase a string (ASCII a-z → A-Z)" },
+  "MINVSCVLA": { "prefix": "MINVSCVLA", "body": "MINVSCVLA", "description": "lowercase a string (ASCII A-Z → a-z)" },
+  "NVMERVS": { "prefix": "NVMERVS", "body": "NVMERVS", "description": "parse a Roman numeral string to an integer" },
+  "ORDINA": { "prefix": "ORDINA", "body": "ORDINA", "description": "sort an array in ascending order" },
+  "PETE": { "prefix": "PETE", "body": "PETE", "description": "HTTP GET request (RETE module)" },
+  "PETITVR": { "prefix": "PETITVR", "body": "PETITVR", "description": "register HTTP GET handler (RETE module)" },
+  "QVAERE": { "prefix": "QVAERE", "body": "QVAERE", "description": "regex findall" },
+  "SCINDE": { "prefix": "SCINDE", "body": "SCINDE", "description": "split a string by delimiter" },
+  "SCRIBE": { "prefix": "SCRIBE", "body": "SCRIBE", "description": "write string to file (SCRIPTA module)" },
+  "SEMEN": { "prefix": "SEMEN", "body": "SEMEN", "description": "seed the random number generator (FORS module)" },
+  "SENATVS": { "prefix": "SENATVS", "body": "SENATVS", "description": "true if a strict majority of booleans are true" },
+  "SVBSTITVE": { "prefix": "SVBSTITVE", "body": "SVBSTITVE", "description": "regex substitute" },
+  "TYPVS": { "prefix": "TYPVS", "body": "TYPVS", "description": "return the type of a value as a string" },
+
+  "FORS": { "prefix": "FORS", "body": "FORS", "description": "randomness module" },
+  "FRACTIO": { "prefix": "FRACTIO", "body": "FRACTIO", "description": "base-12 fractions module" },
+  "MAGNVM": { "prefix": "MAGNVM", "body": "MAGNVM", "description": "large-integer module (thousands suffix _)" },
+  "RETE": { "prefix": "RETE", "body": "RETE", "description": "networking module (HTTP)" },
+  "SCRIPTA": { "prefix": "SCRIPTA", "body": "SCRIPTA", "description": "file I/O module" },
+  "SVBNVLLA": { "prefix": "SVBNVLLA", "body": "SVBNVLLA", "description": "negative-number module (-II syntax)" }
+}

vscode-extension/syntaxes/cent.tmLanguage.json

@@ -45,11 +45,11 @@
 			"patterns": [
 				{
 					"name": "keyword.control.cent",
-					"match": "\\b(AETERNVM|ALIVD|AVGE|AVT|CAPE|CONTINVA|CVM|DEFINI|DESIGNA|DONICVM|DVM|ERVMPE|ET|FAC|FVNCTIO|IN|INVOCA|MINVE|NON|PER|REDI|SI|TABVLA|TEMPTA|TVNC|VSQVE|VT)\\b"
+					"match": "\\b(AETERNVM|ALIVD|AVGE|AVT|CAPE|CONTINVA|CVM|DEFINI|DESIGNA|DIVIDE|DONICVM|DVM|ERVMPE|ET|FAC|FVNCTIO|GRADV|IN|INVOCA|MINVE|MVLTIPLICA|NON|PER|REDI|SI|TABVLA|TEMPTA|TVNC|VSQVE|VT)\\b"
 				},
 				{
 					"name": "keyword.operator.comparison.cent",
-					"match": "\\b(DISPAR|EST|MINVS|PLVS)\\b"
+					"match": "\\b(HAVD_PLVS|HAVD_MINVS|DISPAR|EST|MINVS|PLVS)\\b"
 				},
 				{
 					"name": "keyword.operator.arithmetic.cent",
@@ -65,7 +65,7 @@
 			"patterns": [
 				{
 					"name": "support.function.builtin.cent",
-					"match": "\\b(ADIVNGE|AVDI_NVMERVS|AVDI|AVSCVLTA|CLAVES|DECIMATIO|DIC|DORMI|EVERRE|FORTVITVS_NVMERVS|FORTVITA_ELECTIO|LEGE|LONGITVDO|NVMERVS|ORDINA|PETE|PETITVR|QVAERE|SCINDE|SCRIBE|SEMEN|SENATVS|SVBSTITVE|TYPVS)\\b"
+					"match": "\\b(ADIVNGE|AVDI_NVMERVS|AVDI|AVSCVLTA|CLAVES|DECIMATIO|DIC|DORMI|EVERRE|FORTVITVS_NVMERVS|FORTVITA_ELECTIO|LEGE|LITTERA|LONGITVDO|MAIVSCVLA|MINVSCVLA|NVMERVS|ORDINA|PETE|PETITVR|QVAERE|SCINDE|SCRIBE|SEMEN|SENATVS|SVBSTITVE|TYPVS)\\b"
 				}
 			]
 		},