Arithmetic

compiler/compiler.go

@@ -34,6 +34,7 @@ func (c *Compiler) Compile(node ast.Node) error {
 		if err != nil {
 			return err
 		}
+		c.emit(code.OpPop)
 
 	case *ast.InfixExpression:
 		err := c.Compile(node.Left)
@@ -49,6 +50,12 @@ func (c *Compiler) Compile(node ast.Node) error {
 		switch node.Operator {
 		case "+":
 			c.emit(code.OpAdd)
+		case "-":
+			c.emit(code.OpSub)
+		case "*":
+			c.emit(code.OpMul)
+		case "/":
+			c.emit(code.OpDiv)
 		default:
 			return fmt.Errorf("unknown operator %s", node.Operator)
 		}

compiler/compiler_test.go

@@ -25,6 +25,47 @@ func TestIntegerArithmetic(t *testing.T) {
 				code.Make(code.OpConstant, 0),
 				code.Make(code.OpConstant, 1),
 				code.Make(code.OpAdd),
+				code.Make(code.OpPop),
+			},
+		},
+		{
+			input:             "1; 2",
+			expectedConstants: []interface{}{1, 2},
+			expectedInstructions: []code.Instructions{
+				code.Make(code.OpConstant, 0),
+				code.Make(code.OpPop),
+				code.Make(code.OpConstant, 1),
+				code.Make(code.OpPop),
+			},
+		},
+		{
+			input:             "1 - 2",
+			expectedConstants: []interface{}{1, 2},
+			expectedInstructions: []code.Instructions{
+				code.Make(code.OpConstant, 0),
+				code.Make(code.OpConstant, 1),
+				code.Make(code.OpSub),
+				code.Make(code.OpPop),
+			},
+		},
+		{
+			input:             "1 * 2",
+			expectedConstants: []interface{}{1, 2},
+			expectedInstructions: []code.Instructions{
+				code.Make(code.OpConstant, 0),
+				code.Make(code.OpConstant, 1),
+				code.Make(code.OpMul),
+				code.Make(code.OpPop),
+			},
+		},
+		{
+			input:             "2 / 1",
+			expectedConstants: []interface{}{2, 1},
+			expectedInstructions: []code.Instructions{
+				code.Make(code.OpConstant, 0),
+				code.Make(code.OpConstant, 1),
+				code.Make(code.OpDiv),
+				code.Make(code.OpPop),
 			},
 		},
 	}