🐐 Negation

centvrion/ast_nodes.py

@@ -330,6 +330,18 @@ class BinOp(Node):
         raise Exception(self.op)
 
 
+class UnaryMinus(Node):
+  def __init__(self, expr):
+    self.expr = expr
+
+  def __repr__(self):
+    return f"UnaryMinus({self.expr!r})"
+
+  def _eval(self, vtable):
+    vtable, val = self.expr.eval(vtable)
+    return vtable, ValInt(-val.value())
+
+
 class SiStatement(Node):
   def __init__(self, test, statements, else_part) -> None:
     self.test = test

centvrion/parser.py

@@ -14,7 +14,8 @@ class Parser():
         ('left', ["KEYWORD_ET"]),
         ('left', ["KEYWORD_PLVS", "KEYWORD_MINVS", "KEYWORD_EST"]),
         ('left', ["SYMBOL_PLUS", "SYMBOL_MINUS"]),
-        ('left', ["SYMBOL_TIMES", "SYMBOL_DIVIDE"])
+        ('left', ["SYMBOL_TIMES", "SYMBOL_DIVIDE"]),
+        ('right', ["UMINUS"]),
       ]
     )
 
@@ -173,6 +174,10 @@ class Parser():
     def binop(tokens):
       return ast_nodes.BinOp(tokens[0], tokens[2], tokens[1].name)
 
+    @self.pg.production('expression : SYMBOL_MINUS expression', precedence='UMINUS')
+    def unary_minus(tokens):
+      return ast_nodes.UnaryMinus(tokens[1])
+
     @self.pg.production('expression : KEYWORD_INVOCA id expressions')
     def invoca(tokens):
       return ast_nodes.Invoca(tokens[1], tokens[2])