🐐 DECIMATIO

README.md

@@ -248,12 +248,14 @@ Vnlike many other programming languages with modules, the modules in `CENTVRION`
 ### FORS
 ![CVM FORS](snippets/fors.png)
 
-The `FORS` module allows you to add randomness to your `CENTVRION` program. It adds 3 new built-in functions: `FORTIS_NVMERVS int int`, `FORTIS_ELECTIONIS ['a]`, and `SEMEN int`.
+The `FORS` module allows you to add randomness to your `CENTVRION` program. It adds 4 new built-in functions: `FORTIS_NVMERVS int int`, `FORTIS_ELECTIONIS ['a]`, `DECIMATIO ['a]`, and `SEMEN int`.
 
 `FORTIS_NVMERVS int int` picks a random int in the (inclusive) range of the two given ints.
 
 `FORTIS_ELECTIONIS ['a]` picks a random element from the given array. `FORTIS_ELECTIONIS array` is identical to ```array[FORTIS_NVMERVS NVLLVS ((LONGITVDO array)-I)]```.
 
+`DECIMATIO ['a]` returns a copy of the given array with a random tenth of its elements removed. Arrays with fewer than 10 elements are returned unchanged.
+
 `SEMEN int` seeds the random number generator for reproducibility.
 
 ### FRACTIO

centvrion/ast_nodes.py

@@ -957,6 +957,16 @@ class BuiltIn(Node):
           raise CentvrionError("SEMEN requires an integer seed")
         random.seed(seed)
         return vtable, ValNul()
+      case "DECIMATIO":
+        if "FORS" not in vtable["#modules"]:
+          raise CentvrionError("Cannot use 'DECIMATIO' without module 'FORS'")
+        if not isinstance(params[0], ValList):
+          raise CentvrionError("DECIMATIO requires an array")
+        arr = list(params[0].value())
+        to_remove = len(arr) // 10
+        for _ in range(to_remove):
+          arr.pop(random.randint(0, len(arr) - 1))
+        return vtable, ValList(arr)
       case "LONGITVDO":
         if isinstance(params[0], (ValList, ValStr)):
           return vtable, ValInt(len(params[0].value()))

centvrion/compiler/emit_expr.py

@@ -186,6 +186,13 @@ def _emit_builtin(node, ctx):
       else:
         lines.append(f"CentValue {tmp} = cent_fortis_electionis({param_vars[0]});")
 
+    case "DECIMATIO":
+      if not ctx.has_module("FORS"):
+        lines.append('cent_runtime_error("FORS module required for DECIMATIO");')
+        lines.append(f"CentValue {tmp} = cent_null();")
+      else:
+        lines.append(f"CentValue {tmp} = cent_decimatio({param_vars[0]});")
+
     case "SEMEN":
       if not ctx.has_module("FORS"):
         lines.append('cent_runtime_error("FORS module required for SEMEN");')

centvrion/compiler/runtime/cent_runtime.c

@@ -533,6 +533,25 @@ CentValue cent_fortis_electionis(CentValue lst) {
   return lst.lval.items[rand() % lst.lval.len];
 }
 
+CentValue cent_decimatio(CentValue lst) {
+  if (lst.type != CENT_LIST)
+    cent_type_error("'DECIMATIO' requires a list");
+  int len = lst.lval.len;
+  /* Copy the list so we can remove in-place */
+  CentValue result = cent_list_new(len);
+  for (int i = 0; i < len; i++)
+    cent_list_push(&result, lst.lval.items[i]);
+  int to_remove = result.lval.len / 10;
+  for (int i = 0; i < to_remove; i++) {
+    int idx = rand() % result.lval.len;
+    /* Shift remaining elements left */
+    for (int j = idx; j < result.lval.len - 1; j++)
+      result.lval.items[j] = result.lval.items[j + 1];
+    result.lval.len--;
+  }
+  return result;
+}
+
 void cent_semen(CentValue seed) {
   if (seed.type != CENT_INT)
     cent_type_error("'SEMEN' requires an integer seed");

centvrion/compiler/runtime/cent_runtime.h

@@ -177,6 +177,7 @@ CentValue cent_avdi_numerus(void);                    /* AVDI_NVMERVS */
 CentValue cent_longitudo(CentValue v);                  /* LONGITVDO  */
 CentValue cent_fortis_numerus(CentValue lo, CentValue hi); /* FORTIS_NVMERVS */
 CentValue cent_fortis_electionis(CentValue lst);          /* FORTIS_ELECTIONIS */
+CentValue cent_decimatio(CentValue lst);                       /* DECIMATIO */
 void      cent_semen(CentValue seed);                          /* SEMEN */
 void      cent_everro(void);                                   /* EVERRO */
 

centvrion/lexer.py

@@ -39,6 +39,7 @@ keyword_tokens = [("KEYWORD_"+i, i) for i in [
 builtin_tokens = [("BUILTIN", i) for i in [
   "AVDI_NVMERVS",
   "AVDI",
+  "DECIMATIO",
   "DICE",
   "EVERRO",
   "FORTIS_NVMERVS",

snippets/syntaxes/centvrion.sublime-syntax

@@ -57,7 +57,7 @@ contexts:
       scope: constant.language.centvrion
 
   builtins:
-    - match: '\b(AVDI_NVMERVS|AVDI|DICE|FORTIS_NVMERVS|FORTIS_ELECTIONIS|LONGITVDO|SEMEN)\b'
+    - match: '\b(AVDI_NVMERVS|AVDI|DECIMATIO|DICE|FORTIS_NVMERVS|FORTIS_ELECTIONIS|LONGITVDO|SEMEN)\b'
       scope: support.function.builtin.centvrion
 
   modules:

tests.py

@@ -537,6 +537,14 @@ builtin_tests = [
   ('LONGITVDO("")', Program([], [ExpressionStatement(BuiltIn("LONGITVDO", [String("")]))]), ValInt(0)),
   ("CVM FORS\nFORTIS_ELECTIONIS([I, II, III])", Program([ModuleCall("FORS")], [ExpressionStatement(BuiltIn("FORTIS_ELECTIONIS", [DataArray([Numeral("I"), Numeral("II"), Numeral("III")])]))]), ValInt(1)),
   ("CVM FORS\nSEMEN(XLII)\nFORTIS_NVMERVS(I, C)", Program([ModuleCall("FORS")], [ExpressionStatement(BuiltIn("SEMEN", [Numeral("XLII")])), ExpressionStatement(BuiltIn("FORTIS_NVMERVS", [Numeral("I"), Numeral("C")]))]), ValInt(82)),
+  # DECIMATIO: seed 42, 10 elements → removes 1 (element II)
+  ("CVM FORS\nSEMEN(XLII)\nDECIMATIO([I, II, III, IV, V, VI, VII, VIII, IX, X])", Program([ModuleCall("FORS")], [ExpressionStatement(BuiltIn("SEMEN", [Numeral("XLII")])), ExpressionStatement(BuiltIn("DECIMATIO", [DataArray([Numeral("I"), Numeral("II"), Numeral("III"), Numeral("IV"), Numeral("V"), Numeral("VI"), Numeral("VII"), Numeral("VIII"), Numeral("IX"), Numeral("X")])]))]), ValList([ValInt(1), ValInt(3), ValInt(4), ValInt(5), ValInt(6), ValInt(7), ValInt(8), ValInt(9), ValInt(10)])),
+  # DECIMATIO: seed 1, 3 elements → 3//10=0, nothing removed
+  ("CVM FORS\nSEMEN(I)\nDECIMATIO([I, II, III])", Program([ModuleCall("FORS")], [ExpressionStatement(BuiltIn("SEMEN", [Numeral("I")])), ExpressionStatement(BuiltIn("DECIMATIO", [DataArray([Numeral("I"), Numeral("II"), Numeral("III")])]))]), ValList([ValInt(1), ValInt(2), ValInt(3)])),
+  # DECIMATIO: empty array → empty array
+  ("CVM FORS\nDECIMATIO([])", Program([ModuleCall("FORS")], [ExpressionStatement(BuiltIn("DECIMATIO", [DataArray([])]))]), ValList([])),
+  # DECIMATIO: seed 42, 20 elements → removes 2 (elements I and IV)
+  ("CVM FORS\nSEMEN(XLII)\nDECIMATIO([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("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")])]))]), ValList([ValInt(2), ValInt(3), ValInt(5), ValInt(6), ValInt(7), ValInt(8), ValInt(9), ValInt(10), ValInt(11), ValInt(12), ValInt(13), ValInt(14), ValInt(15), ValInt(16), ValInt(17), ValInt(18), ValInt(19), ValInt(20)])),
 ]
 
 class TestBuiltins(unittest.TestCase):
@@ -577,6 +585,8 @@ error_tests = [
   ("CVM FORS\nFORTIS_ELECTIONIS([])", CentvrionError),                 # FORTIS_ELECTIONIS on empty array
   ("CVM FORS\nFORTIS_NVMERVS(X, I)", CentvrionError),                  # FORTIS_NVMERVS a > b
   ("PER i IN I FACE { DICE(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
   ("DESIGNA x VT I\nINVOCA x ()", CentvrionError),                     # invoking a non-function
   ("SI I TVNC { DESIGNA r VT I }", CentvrionError),                    # non-bool SI condition: int

vscode-extension/syntaxes/cent.tmLanguage.json

@@ -65,7 +65,7 @@
 			"patterns": [
 				{
 					"name": "support.function.builtin.cent",
-					"match": "\\b(AVDI_NVMERVS|AVDI|DICE|EVERRO|FORTIS_NVMERVS|FORTIS_ELECTIONIS|LONGITVDO)\\b"
+					"match": "\\b(AVDI_NVMERVS|AVDI|DECIMATIO|DICE|EVERRO|FORTIS_NVMERVS|FORTIS_ELECTIONIS|LONGITVDO|SEMEN)\\b"
 				}
 			]
 		},