Eval complete

evaluator/evaluator_test.go

@@ -120,7 +120,9 @@ func TestReturnStatements(t *testing.T) {
 		{"return 10; 9;", 10},
 		{"return 2 * 5; 9;", 10},
 		{"9; return 2 * 5; 9;", 10},
-		{`
+		{"if (10 > 1) { return 10; }", 10},
+		{
+			`
 				if (10 > 1) {
 				  if (10 > 1) {
 					return 10;
@@ -128,9 +130,28 @@ func TestReturnStatements(t *testing.T) {
 				
 				  return 1;
 				}
-			`,
+				`,
 			10,
 		},
+		{
+			`
+				let f = fn(x) {
+				  return x;
+				  x + 10;
+				};
+				f(10);`,
+			10,
+		},
+		{
+			`
+				let f = fn(x) {
+				   let result = x + 10;
+				   return result;
+				   return 10;
+				};
+				f(10);`,
+			20,
+		},
 	}
 
 	for _, tt := range tests {
@@ -219,6 +240,60 @@ func TestLetStatements(t *testing.T) {
 	}
 }
 
+func TestFunctionObject(t *testing.T) {
+	input := "fn(x) { x + 2; };"
+
+	evaluated := testEval(input)
+	fn, ok := evaluated.(*object.Function)
+	if !ok {
+		t.Fatalf("object is not Function. got=%T (%+v)", evaluated, evaluated)
+	}
+
+	if len(fn.Parameters) != 1 {
+		t.Fatalf("function has wrong parameters. Parameters=%+v", fn.Parameters)
+	}
+
+	if fn.Parameters[0].String() != "x" {
+		t.Fatalf("parameter is not 'x'. got=%q", fn.Parameters[0])
+	}
+
+	expectedBody := "(x + 2)"
+
+	if fn.Body.String() != expectedBody {
+		t.Fatalf("body is not %q. got=%q", expectedBody, fn.Body.String())
+	}
+}
+
+func TestFunctionApplication(t *testing.T) {
+	tests := []struct {
+		input    string
+		expected int64
+	}{
+		{"let identity = fn(x) { x; }; identity(5);", 5},
+		{"let identity = fn(x) { return x; }; identity(5);", 5},
+		{"let double = fn(x) { x * 2; }; double(5);", 10},
+		{"let add = fn(x, y) { x + y; }; add(5, 5);", 10},
+		{"let add = fn(x, y) { x + y; }; add(5 + 5, add(5, 5));", 20},
+		{"fn(x) { x; }(5)", 5},
+	}
+
+	for _, tt := range tests {
+		testIntegerObject(t, testEval(tt.input), tt.expected)
+	}
+}
+
+func TestClosures(t *testing.T) {
+	input := `
+			let newAdder = fn(x) {
+			  fn(y) { x + y };
+			};
+			
+			let addTwo = newAdder(2);
+			addTwo(2);`
+
+	testIntegerObject(t, testEval(input), 4)
+}
+
 func testEval(input string) object.Object {
 	l := lexer.New(input)
 	p := parser.New(l)