Added overloaded support for str * int

evaluator/evaluator.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"monkey/ast"
 	"monkey/object"
+	"strings"
 )
 
 var (
@@ -304,6 +305,18 @@ func evalIntegerPrefixOperatorExpression(operator string, right object.Object) o
 
 func evalInfixExpression(operator string, left, right object.Object) object.Object {
 	switch {
+
+	// " " * 4
+	case left.Type() == object.STRING_OBJ && right.Type() == object.INTEGER_OBJ:
+		leftVal := left.(*object.String).Value
+		rightVal := right.(*object.Integer).Value
+		return &object.String{Value: strings.Repeat(leftVal, int(rightVal))}
+	// 4 * " "
+	case left.Type() == object.INTEGER_OBJ && right.Type() == object.STRING_OBJ:
+		leftVal := left.(*object.Integer).Value
+		rightVal := right.(*object.String).Value
+		return &object.String{Value: strings.Repeat(rightVal, int(leftVal))}
+
 	case left.Type() == object.BOOLEAN_OBJ && right.Type() == object.BOOLEAN_OBJ:
 		return evalBooleanInfixExpression(operator, left, right)
 	case left.Type() == object.INTEGER_OBJ && right.Type() == object.INTEGER_OBJ:

evaluator/evaluator_test.go

@@ -10,7 +10,7 @@ import (
 	"testing"
 )
 
-func TestEvalIntegerExpression(t *testing.T) {
+func TestEvalExpressions(t *testing.T) {
 	tests := []struct {
 		input    string
 		expected interface{}
@@ -36,6 +36,8 @@ func TestEvalIntegerExpression(t *testing.T) {
 		{"1 | 2", 3},
 		{"2 ^ 4", 6},
 		{"3 & 6", 2},
+		{`" " * 4`, "    "},
+		{`4 * " "`, "    "},
 	}
 
 	for _, tt := range tests {

vm/vm.go

@@ -526,6 +526,18 @@ func (vm *VM) executeBinaryOperation(op code.Opcode) error {
 	rightType := right.Type()
 
 	switch {
+
+	// " " * 4
+	case left.Type() == object.STRING_OBJ && right.Type() == object.INTEGER_OBJ:
+		leftVal := left.(*object.String).Value
+		rightVal := right.(*object.Integer).Value
+		return vm.push(&object.String{Value: strings.Repeat(leftVal, int(rightVal))})
+	// 4 * " "
+	case left.Type() == object.INTEGER_OBJ && right.Type() == object.STRING_OBJ:
+		leftVal := left.(*object.Integer).Value
+		rightVal := right.(*object.String).Value
+		return vm.push(&object.String{Value: strings.Repeat(rightVal, int(leftVal))})
+
 	case leftType == object.BOOLEAN_OBJ && rightType == object.BOOLEAN_OBJ:
 		return vm.executeBinaryBooleanOperation(op, left, right)
 	case leftType == object.INTEGER_OBJ && rightType == object.INTEGER_OBJ:

vm/vm_test.go

@@ -326,6 +326,8 @@ func TestStringExpressions(t *testing.T) {
 		{`"monkey"`, "monkey"},
 		{`"mon" + "key"`, "monkey"},
 		{`"mon" + "key" + "banana"`, "monkeybanana"},
+		{`" " * 4`, "    "},
+		{`4 * " "`, "    "},
 	}
 
 	runVmTests(t, tests)