🐐 PER deconstructing

README.md

@@ -253,6 +253,19 @@ condition. Exit the loop with `ERVMPE` (or `REDI` from inside a function).
 > V
 ```
 
+Variables can be unpacked in `PER` loops, similar to `DESIGNA` destructuring:
+
+```
+PER a, b IN [[I, II], [III, IV]] FAC {
+  DIC(a + b)
+}
+```
+
+```
+> III
+> VII
+```
+
 ## Error handling
 
 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.

centvrion/ast_nodes.py

@@ -1140,6 +1140,10 @@ class PerStatement(Node):
   def __eq__(self, other):
     return type(self) == type(other) and self.data_list == other.data_list and self.variable_name == other.variable_name and self.statements == other.statements
 
+  @property
+  def destructure(self):
+    return isinstance(self.variable_name, list)
+
   def __repr__(self) -> str:
     test = repr(self.data_list)
     variable_name = repr(self.variable_name)
@@ -1149,7 +1153,23 @@ class PerStatement(Node):
 
   def print(self):
     body = "\n".join(s.print() for s in self.statements)
-    return f"PER {self.variable_name.print()} IN {self.data_list.print()} FAC {{\n{body}\n}}"
+    if self.destructure:
+      var_str = ", ".join(v.print() for v in self.variable_name)
+    else:
+      var_str = self.variable_name.print()
+    return f"PER {var_str} IN {self.data_list.print()} FAC {{\n{body}\n}}"
+
+  def _assign_loop_var(self, vtable, item):
+    if self.destructure:
+      if not isinstance(item, ValList):
+        raise CentvrionError("Cannot destructure non-array value in PER loop")
+      if len(item.value()) != len(self.variable_name):
+        raise CentvrionError(
+          f"Destructuring mismatch: {len(self.variable_name)} targets, {len(item.value())} values")
+      for id_node, val in zip(self.variable_name, item.value()):
+        vtable[id_node.name] = val
+    else:
+      vtable[self.variable_name.name] = item
 
   def _eval(self, vtable):
     vtable, array = self.data_list.eval(vtable)
@@ -1158,10 +1178,9 @@ class PerStatement(Node):
       array = ValList(keys)
     if not isinstance(array, ValList):
       raise CentvrionError("PER requires an array or dict")
-    variable_name = self.variable_name.name
     last_val = ValNul()
     for item in array:
-      vtable[variable_name] = item
+      self._assign_loop_var(vtable, item)
       for statement in self.statements:
         vtable, val = statement.eval(vtable)
         if vtable["#break"] or vtable["#continue"] or vtable["#return"] is not None:

centvrion/compiler/emit_stmt.py

@@ -65,23 +65,44 @@ def emit_stmt(node, ctx):
   if isinstance(node, PerStatement):
     arr_lines, arr_var = emit_expr(node.data_list, ctx)
     i_var = ctx.fresh_tmp()
-    var_name = node.variable_name.name
     body_lines = _emit_body(node.statements, ctx)
-    lines = arr_lines + [
+
-      f"if ({arr_var}.type == CENT_DICT) {{",
+    if node.destructure:
-      f"  for (int {i_var} = 0; {i_var} < {arr_var}.dval.len; {i_var}++) {{",
+      # Destructuring PER — each element must be a list
-      f'    cent_scope_set(&_scope, "{var_name}", {arr_var}.dval.keys[{i_var}]);',
+      elem_var = ctx.fresh_tmp()
-    ]
+      assign_lines = [
-    lines += [f"    {l}" for l in body_lines]
+        f"CentValue {elem_var} = {arr_var}.lval.items[{i_var}];",
-    lines += [
+        f'if ({elem_var}.type != CENT_LIST) cent_type_error("Cannot destructure non-array value in PER loop");',
-      "  }",
+        f'if ({elem_var}.lval.len != {len(node.variable_name)}) cent_runtime_error("Destructuring mismatch");',
-      "} else {",
+      ]
-      f'  if ({arr_var}.type != CENT_LIST) cent_type_error("PER requires an array or dict");',
+      for j, id_node in enumerate(node.variable_name):
-      f"  for (int {i_var} = 0; {i_var} < {arr_var}.lval.len; {i_var}++) {{",
+        tmp = ctx.fresh_tmp()
-      f'    cent_scope_set(&_scope, "{var_name}", {arr_var}.lval.items[{i_var}]);',
+        assign_lines.append(f"CentValue {tmp} = cent_list_index({elem_var}, cent_int({j + 1}));")
-    ]
+        assign_lines.append(f'cent_scope_set(&_scope, "{id_node.name}", {tmp});')
-    lines += [f"    {l}" for l in body_lines]
+      lines = arr_lines + [
-    lines += ["  }", "}"]
+        f'if ({arr_var}.type != CENT_LIST) cent_type_error("PER requires an array");',
+        f"for (int {i_var} = 0; {i_var} < {arr_var}.lval.len; {i_var}++) {{",
+      ]
+      lines += [f"  {l}" for l in assign_lines]
+      lines += [f"  {l}" for l in body_lines]
+      lines += ["}"]
+    else:
+      var_name = node.variable_name.name
+      lines = arr_lines + [
+        f"if ({arr_var}.type == CENT_DICT) {{",
+        f"  for (int {i_var} = 0; {i_var} < {arr_var}.dval.len; {i_var}++) {{",
+        f'    cent_scope_set(&_scope, "{var_name}", {arr_var}.dval.keys[{i_var}]);',
+      ]
+      lines += [f"    {l}" for l in body_lines]
+      lines += [
+        "  }",
+        "} else {",
+        f'  if ({arr_var}.type != CENT_LIST) cent_type_error("PER requires an array or dict");',
+        f"  for (int {i_var} = 0; {i_var} < {arr_var}.lval.len; {i_var}++) {{",
+        f'    cent_scope_set(&_scope, "{var_name}", {arr_var}.lval.items[{i_var}]);',
+      ]
+      lines += [f"    {l}" for l in body_lines]
+      lines += ["  }", "}"]
     return lines
 
   if isinstance(node, Defini):

centvrion/parser.py

@@ -242,6 +242,10 @@ class Parser():
     def aeternvm(tokens):
       return ast_nodes.DumStatement(ast_nodes.Bool(False), tokens[3])
 
+    @self.pg.production('per_statement : KEYWORD_PER id SYMBOL_COMMA id_list_rest KEYWORD_IN expression KEYWORD_FAC SYMBOL_LCURL statements SYMBOL_RCURL')
+    def per_destructure(tokens):
+      return ast_nodes.PerStatement(tokens[5], [tokens[1]] + tokens[3], tokens[8])
+
     @self.pg.production('per_statement : KEYWORD_PER id KEYWORD_IN expression KEYWORD_FAC SYMBOL_LCURL statements SYMBOL_RCURL')
     def per(tokens):
       return ast_nodes.PerStatement(tokens[3], tokens[1], tokens[6])

language/main.tex

@@ -38,6 +38,7 @@
         \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{REDI(} \textit{optional-expressions} \texttt{)}} \\
         \languageline{statement}{\texttt{ERVMPE}} \\

tests.py

@@ -473,6 +473,20 @@ control_tests = [
   ("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):
@@ -754,6 +768,8 @@ error_tests = [
   ("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
@@ -1549,6 +1565,31 @@ loop_edge_tests = [
                    [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
 ]
 
 class TestLoopEdge(unittest.TestCase):