comparison operators, part 1

src/chunk.zig

@@ -20,6 +20,11 @@ const AllOpcodes = struct {
     pub False: u8 = 10,
 
     pub Not: u8 = 11,
+
+    // comparison op codes!
+    pub Equal: u8 = 12,
+    pub Greater: u8 = 13,
+    pub Less: u8 = 14,
 };
 
 pub const OpCode = AllOpcodes{};

src/compiler.zig

@@ -77,16 +77,16 @@ var rules = []ParseRule{
     // as the token enum says, those are 1/2 char tokens.
     ParseRule{ .prefix = Compiler.unary },
     // this is specifically for the != operator
-    ParseRule{ .precedence = .Equality },
+    ParseRule{ .infix = Compiler.binary, .precedence = .Equality },
     ParseRule{},
     // this is specifically for the == operator
-    ParseRule{ .precedence = .Equality },
+    ParseRule{ .infix = Compiler.binary, .precedence = .Equality },
 
     // all the comparison ones
-    ParseRule{ .precedence = .Comparison },
-    ParseRule{ .precedence = .Comparison },
-    ParseRule{ .precedence = .Comparison },
-    ParseRule{ .precedence = .Comparison },
+    ParseRule{ .infix = Compiler.binary, .precedence = .Comparison },
+    ParseRule{ .infix = Compiler.binary, .precedence = .Comparison },
+    ParseRule{ .infix = Compiler.binary, .precedence = .Comparison },
+    ParseRule{ .infix = Compiler.binary, .precedence = .Comparison },
 
     ParseRule{},
     ParseRule{},
@@ -190,7 +190,7 @@ pub const Compiler = struct {
         try self.currentChunk().write(byte, self.parser.previous.line);
     }
 
-    fn emitBytes(self: *Compiler, byte1: u8, byte2: u82) !void {
+    fn emitBytes(self: *Compiler, byte1: u8, byte2: u8) !void {
         try self.emitByte(byte1);
         try self.emitByte(byte2);
     }
@@ -251,6 +251,15 @@ pub const Compiler = struct {
             .MINUS => try self.emitByte(OpCode.Subtract),
             .STAR => try self.emitByte(OpCode.Multiply),
             .SLASH => try self.emitByte(OpCode.Divide),
+
+            .EQUAL_EQUAL => try self.emitByte(OpCode.Equal),
+            .GREATER => try self.emitByte(OpCode.Greater),
+            .LESS => try self.emitByte(OpCode.Less),
+
+            .BANG_EQUAL => try self.emitBytes(OpCode.Equal, OpCode.Not),
+            .GREATER_EQUAL => try self.emitBytes(OpCode.Less, OpCode.Not),
+            .LESS_EQUAL => try self.emitBytes(OpCode.Greater, OpCode.Not),
+
             else => unreachable,
         }
     }

src/vm.zig

@@ -20,6 +20,16 @@ fn isFalsey(val: value.Value) bool {
     return val.vtype == .Nil or (val.vtype == .Bool and !val.as.Bool);
 }
 
+fn valuesEqual(a: value.Value, b: value.Value) bool {
+    if (a.vtype != b.vtype) return false;
+
+    switch (a.vtype) {
+        .Nil => return true,
+        .Bool => return a.as.Bool == b.as.Bool,
+        .Number => return a.as.Number == b.as.Number,
+    }
+}
+
 pub const VM = struct {
     chk: *Chunk = undefined,
     src: []const u8,
@@ -170,6 +180,12 @@ pub const VM = struct {
                 chunk.OpCode.True => try self.push(values.BoolVal(true)),
                 chunk.OpCode.False => try self.push(values.BoolVal(false)),
 
+                chunk.OpCode.Equal => blk: {
+                    var a = self.pop();
+                    var b = self.pop();
+                    try self.push(values.BoolVal(valuesEqual(a, b)));
+                },
+
                 chunk.OpCode.Add => try self.doAdd(),
                 chunk.OpCode.Subtract => try self.doSub(),
                 chunk.OpCode.Multiply => try self.doMul(),
@@ -177,6 +193,7 @@ pub const VM = struct {
                 chunk.OpCode.Not => blk: {
                     try self.push(values.BoolVal(isFalsey(self.pop())));
                 },
+
                 chunk.OpCode.Negate => blk: {
                     var val = self.peek(0);
                     if (val.vtype != .Bool) {