🐐 Unpacking arrays

centvrion/ast_nodes.py

@@ -431,6 +431,35 @@ class DesignaIndex(Node):
     return vtable, ValNul()
 
 
+class DesignaDestructure(Node):
+  def __init__(self, variables: list, value: Node) -> None:
+    self.ids = variables
+    self.value = value
+
+  def __eq__(self, other):
+    return type(self) == type(other) and self.ids == other.ids and self.value == other.value
+
+  def __repr__(self) -> str:
+    ids_string = ", ".join(repr(i) for i in self.ids)
+    value_string = repr(self.value).replace('\n', '\n  ')
+    return f"DesignaDestructure(\n  [{ids_string}],\n  {value_string}\n)"
+
+  def print(self):
+    ids_str = ", ".join(i.print() for i in self.ids)
+    return f"DESIGNA {ids_str} VT {self.value.print()}"
+
+  def _eval(self, vtable):
+    vtable, val = self.value.eval(vtable)
+    if not isinstance(val, ValList):
+      raise CentvrionError("Cannot destructure non-array value")
+    if len(val.value()) != len(self.ids):
+      raise CentvrionError(
+        f"Destructuring mismatch: {len(self.ids)} targets, {len(val.value())} values")
+    for id_node, item in zip(self.ids, val.value()):
+      vtable[id_node.name] = item
+    return vtable, ValNul()
+
+
 class Defini(Node):
   def __init__(self, name: ID, parameters: list[ID], statements: list[Node]) -> None:
     self.name = name

centvrion/compiler/emit_stmt.py

@@ -1,6 +1,6 @@
 from centvrion.ast_nodes import (
-  Designa, DesignaIndex, SiStatement, DumStatement, PerStatement,
-  Defini, Redi, Erumpe, Continva, ExpressionStatement, ID,
+  Designa, DesignaIndex, DesignaDestructure, SiStatement, DumStatement,
+  PerStatement, Defini, Redi, Erumpe, Continva, ExpressionStatement, ID,
 )
 from centvrion.compiler.emit_expr import emit_expr
 
@@ -29,6 +29,18 @@ def emit_stmt(node, ctx):
       ]
     )
 
+  if isinstance(node, DesignaDestructure):
+    n = len(node.ids)
+    val_lines, val_var = emit_expr(node.value, ctx)
+    lines = val_lines[:]
+    lines.append(f'if ({val_var}.type != CENT_LIST) cent_type_error("Cannot destructure non-array value");')
+    lines.append(f'if ({val_var}.lval.len != {n}) cent_runtime_error("Destructuring mismatch");')
+    for i, id_node in enumerate(node.ids):
+      tmp = ctx.fresh_tmp()
+      lines.append(f"CentValue {tmp} = cent_list_index({val_var}, cent_int({i + 1}));")
+      lines.append(f'cent_scope_set(&_scope, "{id_node.name}", {tmp});')
+    return lines
+
   if isinstance(node, SiStatement):
     cond_lines, cond_var = emit_expr(node.test, ctx)
     then_lines = _emit_body(node.statements, ctx)

centvrion/parser.py

@@ -74,6 +74,10 @@ class Parser():
     def statement_designa_index(tokens):
       return ast_nodes.DesignaIndex(tokens[1], tokens[3], tokens[6])
 
+    @self.pg.production('statement : KEYWORD_DESIGNA id SYMBOL_COMMA id_list_rest KEYWORD_VT expression')
+    def statement_designa_destructure(tokens):
+      return ast_nodes.DesignaDestructure([tokens[1]] + tokens[3], tokens[5])
+
     @self.pg.production('statement : id KEYWORD_AVGE expression')
     def statement_avge(tokens):
       return ast_nodes.Designa(tokens[0], ast_nodes.BinOp(tokens[0], tokens[2], "SYMBOL_PLUS"))
@@ -258,6 +262,14 @@ class Parser():
       else:
         return [calls[0]] + calls[2]
 
+    @self.pg.production('id_list_rest : id')
+    @self.pg.production('id_list_rest : id SYMBOL_COMMA id_list_rest')
+    def id_list_rest(calls):
+      if len(calls) == 1:
+        return [calls[0]]
+      else:
+        return [calls[0]] + calls[2]
+
     @self.pg.production("id : ID")
     def id_expression(tokens):
       return ast_nodes.ID(tokens[0].value)