Feature: Add support for negation

2 files changed, 9 insertions, 5 deletions

diff --git a/src/evaluator.zig b/src/evaluator.zig
index 9f8b61f..798d66c 100644
--- a/src/evaluator.zig
+++ b/src/evaluator.zig
@@ -174,6 +174,10 @@ pub const Evaluator = struct {
             },
             .UNARY_EXPRESSION => |x| {
                 const val = try self.get_expression_value(x.expression) orelse return EvaluatorError.EvaluationError;
+                if (!x.negation) {
+                    std.debug.assert(val.* == .NUMBER);
+                    return try self.create_variable(.{ .NUMBER = -val.NUMBER });
+                }
                 std.debug.assert(val.* == .BOOLEAN);
                 return try self.create_variable(.{ .BOOLEAN = !val.BOOLEAN });
             },
@@ -268,7 +272,6 @@ const Environment = struct {
             .allocator = allocator,
         };
 
-        //TODO: Add more scopes when evaluating functions
         // Create global scope
         try self.create_scope();
 
diff --git a/src/parser.zig b/src/parser.zig
index 966cad3..b407c42 100644
--- a/src/parser.zig
+++ b/src/parser.zig
@@ -322,18 +322,19 @@ pub const Parser = struct {
         return lhs;
     }
 
-    // UnaryExpression ::= "!" UnaryExpression | PrimaryExpression
+    // UnaryExpression ::= ("!" | "-") UnaryExpression | PrimaryExpression
     fn parse_unary_expression(self: *Parser) ParserError!*Node {
         errdefer if (!self.try_context) std.debug.print("Error parsing unary expression\n", .{});
 
-        const negation = self.accept_token(tokenizer.TokenType.BANG) != null;
+        const not = self.accept_token(tokenizer.TokenType.BANG) != null;
+        const minus = self.accept_token(tokenizer.TokenType.MINUS) != null;
 
-        if (!negation) {
+        if (!not and !minus) {
             return try self.parse_primary_expression();
         }
 
         return self.create_node(.{ .UNARY_EXPRESSION = .{
-            .negation = negation,
+            .negation = not,
             .expression = try self.parse_unary_expression(),
         } });
     }