From d38f4dec8a1ab01f32964161f138261356ad9a59 Mon Sep 17 00:00:00 2001
From: tijani <tijani@tijanilawal.com>
Date: Thu, 18 Aug 2022 14:32:13 +0000
Subject: [PATCH] Tests - Ensure value producing expression in a let statement
 and also identifiers bound to a variable name. - Tests to ensure valid errors
 with unbound identifiers

git-svn-id: https://svn.tlawal.org/svn/monkey@51 f6afcba9-9ef1-4bdd-9b72-7484f5705bac
---
 evaluator/evaluator.go      | 38 +++++++++++++++++++++----------------
 evaluator/evaluator_test.go | 18 ++++++++++++++++++
 2 files changed, 40 insertions(+), 16 deletions(-)

diff --git a/evaluator/evaluator.go b/evaluator/evaluator.go
index 884787e..c8de3fc 100644
--- a/evaluator/evaluator.go
+++ b/evaluator/evaluator.go
@@ -18,9 +18,25 @@ func Eval(node ast.Node) object.Object {
 	case *ast.Program:
 		return eval_program(node)
 
+	case *ast.BlockStatement:
+		return eval_block_statement(node)
+
 	case *ast.ExpressionStatement:
 		return Eval(node.Expression)
 
+	case *ast.ReturnStatement:
+		val := Eval(node.ReturnValue)
+		if is_error(val) {
+			return val
+		}
+		return &object.ReturnValue{Value: val}
+
+	case *ast.LetStatement:
+		val := Eval(node.Value)
+		if is_error(val) {
+			return val
+		}
+
 		// Expressions
 	case *ast.IntegerLiteral:
 		return &object.Integer{Value: node.Value}
@@ -30,35 +46,25 @@ func Eval(node ast.Node) object.Object {
 
 	case *ast.PrefixExpression:
 		right := Eval(node.Right)
-		if is_error(right){
+		if is_error(right) {
 			return right
 		}
 		return eval_prefix_expression(node.Operator, right)
 
 	case *ast.InfixExpression:
 		left := Eval(node.Left)
-		if is_error(left){
+		if is_error(left) {
 			return left
 		}
-		
+
 		right := Eval(node.Right)
-		if is_error(right){
+		if is_error(right) {
 			return right
 		}
 		return eval_infix_expression(node.Operator, left, right)
 
-	case *ast.BlockStatement:
-		return eval_block_statement(node)
-
 	case *ast.IfExpression:
 		return eval_if_expression(node)
-
-	case *ast.ReturnStatement:
-		val := Eval(node.ReturnValue)
-		if is_error(val){
-			return val
-		}
-		return &object.ReturnValue{Value: val}
 	}
 
 	return nil
@@ -196,10 +202,10 @@ func eval_integer_infix_expression(operator string, left object.Object, right ob
 func eval_if_expression(ie *ast.IfExpression) object.Object {
 	condition := Eval(ie.Condition)
 
-	if is_error(condition){
+	if is_error(condition) {
 		return condition
 	}
-	
+
 	if is_truthy(condition) {
 		return Eval(ie.Consequence)
 	} else if ie.Alternative != nil {
diff --git a/evaluator/evaluator_test.go b/evaluator/evaluator_test.go
index ee6b70e..a43f594 100644
--- a/evaluator/evaluator_test.go
+++ b/evaluator/evaluator_test.go
@@ -55,6 +55,7 @@ func TestErrorHandling(l_test *testing.T) {
         return 1;
        }
       `, "unknown operator: BOOLEAN + BOOLEAN"},
+		{"foobar", "identifier not found:foobar"},
 	}
 
 	for _, tt := range tests {
@@ -167,6 +168,23 @@ func TestReturnStatements(l_test *testing.T) {
 	}
 }
 
+func TestLetStatements(l_test *testing.T) {
+	tests := []struct {
+		input    string
+		expected int64
+	}{
+		{"let a = 5; a;", 5},
+		{"let a = 5 * 5; a;", 25},
+		{"let a = 5; let b = a; b", 5},
+		{"let a = 5; let b = a; let c = a + b + 5", 15},
+	}
+
+	for _, tt := range tests {
+		evaluated := test_eval(tt.input)
+		test_integer_object(l_test, evaluated, tt.expected)
+	}
+}
+
 // Helpers
 func test_eval(input string) object.Object {
 	l_lexer := lexer.New(input)