assert and test changes

compiler/compiler.go

@@ -91,9 +91,7 @@ func (c *Compiler) Compile(node ast.Node) error {
 			return err
 		}
 
-		if !c.lastInstructionIs(code.OpNoop) {
 		c.emit(code.OpPop)
-		}
 
 	case *ast.InfixExpression:
 		if node.Operator == "<" || node.Operator == "<=" {
@@ -182,9 +180,6 @@ func (c *Compiler) Compile(node ast.Node) error {
 		}
 
 	case *ast.IfExpression:
-		if c.lastInstructionIs(code.OpPop) {
-			c.removeLastPop()
-		}
 		c.l++
 		err := c.Compile(node.Condition)
 		c.l--
@@ -240,6 +235,14 @@ func (c *Compiler) Compile(node ast.Node) error {
 		}
 		c.l--
 
+		if c.lastInstructionIs(code.OpPop) {
+			c.removeLastPop()
+		} else {
+			if !c.lastInstructionIs(code.OpReturn) {
+				c.emit(code.OpNull)
+			}
+		}
+
 	case *ast.AssignmentStatement:
 		symbol, ok := c.symbolTable.Resolve(node.Name.Value)
 		if !ok {
@@ -366,8 +369,13 @@ func (c *Compiler) Compile(node ast.Node) error {
 		if c.lastInstructionIs(code.OpPop) {
 			c.replaceLastPopWithReturn()
 		}
+
+		// If the function doesn't end with a return statement add one with a
+		// `return null;` and also handle the edge-case of empty functions.
 		if !c.lastInstructionIs(code.OpReturn) {
+			if !c.lastInstructionIs(code.OpNull) {
 				c.emit(code.OpNull)
+			}
 			c.emit(code.OpReturn)
 		}
 

compiler/compiler_test.go

@@ -231,15 +231,15 @@ func TestConditionals(t *testing.T) {
 				code.Make(code.OpJumpNotTruthy, 10),
 				// 0004
 				code.Make(code.OpConstant, 0),
-				// 0007
+				// 0008
 				code.Make(code.OpJump, 13),
-				// 0010
+				// 0011
 				code.Make(code.OpConstant, 1),
 				// 0013
 				code.Make(code.OpPop),
 				// 0014
 				code.Make(code.OpConstant, 2),
-				// 0017
+				// 0018
 				code.Make(code.OpPop),
 			},
 		},
@@ -256,28 +256,34 @@ func TestConditionals(t *testing.T) {
 				// 0006
 				code.Make(code.OpTrue),
 				// 0007
-				code.Make(code.OpJumpNotTruthy, 19),
+				code.Make(code.OpJumpNotTruthy, 20),
 				// 0010
 				code.Make(code.OpConstant, 1),
 				// 0013
 				code.Make(code.OpAssignGlobal, 0),
 				// 0016
-				code.Make(code.OpJump, 20),
-				// 0019
 				code.Make(code.OpNull),
+				// 0017
+				code.Make(code.OpJump, 21),
 				// 0020
-				code.Make(code.OpFalse),
-				// 0021
-				code.Make(code.OpJumpNotTruthy, 33),
-				// 0024
-				code.Make(code.OpConstant, 2),
-				// 0027
-				code.Make(code.OpAssignGlobal, 0),
-				// 0030
-				code.Make(code.OpJump, 34),
-				// 0033
 				code.Make(code.OpNull),
-				// 0034
+				// 0021
+				code.Make(code.OpPop),
+				// 0022
+				code.Make(code.OpFalse),
+				// 0023
+				code.Make(code.OpJumpNotTruthy, 36),
+				// 0025
+				code.Make(code.OpConstant, 2),
+				// 0029
+				code.Make(code.OpAssignGlobal, 0),
+				// 0032
+				code.Make(code.OpNull),
+				// 0033
+				code.Make(code.OpJump, 37),
+				// 0036
+				code.Make(code.OpNull),
+				// 0037
 				code.Make(code.OpPop),
 			},
 		},
@@ -487,7 +493,7 @@ func TestIndexExpressions(t *testing.T) {
 func TestFunctions(t *testing.T) {
 	tests := []compilerTestCase{
 		{
-			input: "fn() { return 5 + 10 }",
+			input: `fn() { return 5 + 10 }`,
 			expectedConstants: []interface{}{
 				5,
 				10,
@@ -504,24 +510,7 @@ func TestFunctions(t *testing.T) {
 			},
 		},
 		{
-			input: `fn() { 5 + 10 }`,
+			input: `fn() { 1; return 2 }`,
-			expectedConstants: []interface{}{
-				5,
-				10,
-				[]code.Instructions{
-					code.Make(code.OpConstant, 0),
-					code.Make(code.OpConstant, 1),
-					code.Make(code.OpAdd),
-					code.Make(code.OpReturn),
-				},
-			},
-			expectedInstructions: []code.Instructions{
-				code.Make(code.OpClosure, 2, 0),
-				code.Make(code.OpPop),
-			},
-		},
-		{
-			input: `fn() { 1; 2 }`,
 			expectedConstants: []interface{}{
 				1,
 				2,
@@ -566,8 +555,8 @@ func TestClosures(t *testing.T) {
 	tests := []compilerTestCase{
 		{
 			input: `fn(a) { 
-				fn(b) {
+				return fn(b) {
-					a + b
+					return a + b
 				}
 			}
 			`,
@@ -592,9 +581,9 @@ func TestClosures(t *testing.T) {
 		{
 			input: `
             fn(a) {
-                fn(b) {
+                return fn(b) {
-                    fn(c) {
+                    return fn(c) {
-                        a + b + c
+                        return a + b + c
                     }
                 }
             };
@@ -632,13 +621,13 @@ func TestClosures(t *testing.T) {
             fn() {
                 let a = 66;
 
-                fn() {
+                return fn() {
                     let b = 77;
 
-                    fn() {
+                    return fn() {
                         let c = 88;
 
-                        global + a + b + c;
+                        return global + a + b + c;
                     }
                 }
             }
@@ -737,7 +726,7 @@ func TestCompilerScopes(t *testing.T) {
 func TestFunctionCalls(t *testing.T) {
 	tests := []compilerTestCase{
 		{
-			input: `fn() { 24 }();`,
+			input: `fn() { return 24 }();`,
 			expectedConstants: []interface{}{
 				24,
 				[]code.Instructions{
@@ -753,7 +742,7 @@ func TestFunctionCalls(t *testing.T) {
 		},
 		{
 			input: `
-            let noArg = fn() { 24 };
+            let noArg = fn() { return 24 };
             noArg();
             `,
 			expectedConstants: []interface{}{
@@ -773,7 +762,7 @@ func TestFunctionCalls(t *testing.T) {
 		},
 		{
 			input: `
-            let oneArg = fn(a) { a };
+            let oneArg = fn(a) { return a };
             oneArg(24);
             `,
 			expectedConstants: []interface{}{
@@ -794,7 +783,7 @@ func TestFunctionCalls(t *testing.T) {
 		},
 		{
 			input: `
-            let manyArg = fn(a, b, c) { a; b; c };
+            let manyArg = fn(a, b, c) { a; b; return c };
             manyArg(24, 25, 26);
             `,
 			expectedConstants: []interface{}{
@@ -881,7 +870,7 @@ func TestLetStatementScopes(t *testing.T) {
 		{
 			input: `
             let num = 55;
-            fn() { num }
+            fn() { return num }
             `,
 			expectedConstants: []interface{}{
 				55,
@@ -901,7 +890,7 @@ func TestLetStatementScopes(t *testing.T) {
 			input: `
             fn() {
                 let num = 55;
-                num
+                return num
             }
             `,
 			expectedConstants: []interface{}{
@@ -923,7 +912,7 @@ func TestLetStatementScopes(t *testing.T) {
             fn() {
                 let a = 55;
                 let b = 77;
-                a + b
+                return a + b
             }
             `,
 			expectedConstants: []interface{}{
@@ -977,11 +966,11 @@ func TestBuiltins(t *testing.T) {
             `,
 			expectedConstants: []interface{}{1},
 			expectedInstructions: []code.Instructions{
-				code.Make(code.OpGetBuiltin, 4),
+				code.Make(code.OpGetBuiltin, 5),
 				code.Make(code.OpArray, 0),
 				code.Make(code.OpCall, 1),
 				code.Make(code.OpPop),
-				code.Make(code.OpGetBuiltin, 7),
+				code.Make(code.OpGetBuiltin, 8),
 				code.Make(code.OpArray, 0),
 				code.Make(code.OpConstant, 0),
 				code.Make(code.OpCall, 2),
@@ -989,10 +978,10 @@ func TestBuiltins(t *testing.T) {
 			},
 		},
 		{
-			input: `fn() { len([]) }`,
+			input: `fn() { return len([]) }`,
 			expectedConstants: []interface{}{
 				[]code.Instructions{
-					code.Make(code.OpGetBuiltin, 4),
+					code.Make(code.OpGetBuiltin, 5),
 					code.Make(code.OpArray, 0),
 					code.Make(code.OpCall, 1),
 					code.Make(code.OpReturn),
@@ -1012,7 +1001,7 @@ func TestRecursiveFunctions(t *testing.T) {
 	tests := []compilerTestCase{
 		{
 			input: `
-            let countDown = fn(x) { countDown(x - 1); };
+           let countDown = fn(x) { return countDown(x - 1); };
            countDown(1);
            `,
 			expectedConstants: []interface{}{
@@ -1039,8 +1028,8 @@ func TestRecursiveFunctions(t *testing.T) {
 		{
 			input: `
            let wrapper = fn() {
-                let countDown = fn(x) { countDown(x - 1); };
+               let countDown = fn(x) { return countDown(x - 1); };
-                countDown(1);
+               return countDown(1);
            };
            wrapper();
            `,
@@ -1088,15 +1077,15 @@ func TestIteration(t *testing.T) {
 				// 0000
 				code.Make(code.OpTrue),
 				// 0001
-				code.Make(code.OpJumpNotTruthy, 11),
+				code.Make(code.OpJumpNotTruthy, 10),
 				// 0004
 				code.Make(code.OpConstant, 0),
 				// 0007
-				code.Make(code.OpPop),
-				// 0008
 				code.Make(code.OpJump, 0),
-				// 0011
+				// 0010
 				code.Make(code.OpNoop),
+				// 0011
+				code.Make(code.OpPop),
 			},
 		},
 	}

examples/demo.monkey

@@ -40,4 +40,4 @@ let map = fn(arr, f) {
 };
 
 let numbers = [1, 1 + 1, 4 - 1, 2 * 2, 2 + 3, 12 / 2];
-//map(numbers, fibonacci);
+map(numbers, fibonacci);

examples/fact.monkey

@@ -5,4 +5,4 @@ let fact = fn(n) {
   return n * fact(n - 1)
 }
 
-print(fact(5)
+assert(fact(5) == 120, "fact(5) != 120")

object/builtins.go

@@ -20,6 +20,7 @@ var Builtins = map[string]*Builtin{
 	"push":   {Name: "push", Fn: Push},
 	"pop":    {Name: "pop", Fn: Pop},
 	"exit":   {Name: "exit", Fn: Exit},
+	"assert": {Name: "assert", Fn: Assert},
 }
 
 // BuiltinsIndex ...
@@ -213,3 +214,26 @@ func Exit(args ...Object) Object {
 	}
 	return nil
 }
+
+// Assert ...
+func Assert(args ...Object) Object {
+	if len(args) != 2 {
+		return newError("wrong number of arguments. got=%d, want=2",
+			len(args))
+	}
+	if args[0].Type() != BOOLEAN_OBJ {
+		return newError("argument #1 to `assert` must be BOOLEAN, got %s",
+			args[0].Type())
+	}
+	if args[1].Type() != STRING_OBJ {
+		return newError("argument #2 to `assert` must be STRING, got %s",
+			args[0].Type())
+	}
+
+	if !args[0].(*Boolean).Value {
+		fmt.Printf("Assertion Error: %s", args[1].(*String).Value)
+		os.Exit(1)
+	}
+
+	return nil
+}

vm/vm.go

@@ -119,11 +119,7 @@ func (vm *VM) Run() error {
 			}
 
 		case code.OpPop:
-			// This makes things like this work:
-			// >> let x = 1; if (x == 1) { x = 2 }
-			if vm.sp > 0 {
 			vm.pop()
-			}
 
 		case code.OpTrue:
 			err := vm.push(True)

vm/vm_test.go

@@ -259,7 +259,12 @@ func TestConditionals(t *testing.T) {
 		{"if (1 > 2) { 10 } else { 20 }", 20},
 		{"if (1 > 2) { 10 }", Null},
 		{"if (false) { 10 }", Null},
-		//{"if ((if (false) { 10 })) { 10 } else { 20 }", 20},
+		{"if ((if (false) { 10 })) { 10 } else { 20 }", 20},
+		{"if (true) { let a = 5; }", Null},
+		{"if (true) { 10; let a = 5; }", Null},
+		{"if (false) { 10 } else { let b = 5; }", Null},
+		{"if (false) { 10 } else { 10; let b = 5; }", Null},
+		{"if (true) { let a = 5; } else { 10 }", Null},
 		{"let x = 0; if (true) { x = 1; }; if (false) { x = 2; }; x", 1},
 	}
 
@@ -346,24 +351,24 @@ func TestCallingFunctionsWithoutArguments(t *testing.T) {
 	tests := []vmTestCase{
 		{
 			input: `
-        let fivePlusTen = fn() { 5 + 10; };
+        let fivePlusTen = fn() { return 5 + 10; };
         fivePlusTen();
         `,
 			expected: 15,
 		},
 		{
 			input: `
-        let one = fn() { 1; };
+        let one = fn() { return 1; };
-        let two = fn() { 2; };
+        let two = fn() { return 2; };
         one() + two()
         `,
 			expected: 3,
 		},
 		{
 			input: `
-        let a = fn() { 1 };
+        let a = fn() { return 1 };
-        let b = fn() { a() + 1 };
+        let b = fn() { return a() + 1 };
-        let c = fn() { b() + 1 };
+        let c = fn() { return b() + 1 };
         c();
         `,
 			expected: 3,
@@ -421,8 +426,8 @@ func TestFirstClassFunctions(t *testing.T) {
 	tests := []vmTestCase{
 		{
 			input: `
-        let returnsOne = fn() { 1; };
+        let returnsOne = fn() { return 1; };
-        let returnsOneReturner = fn() { returnsOne; };
+        let returnsOneReturner = fn() { return returnsOne; };
         returnsOneReturner()();
         `,
 			expected: 1,
@@ -430,7 +435,7 @@ func TestFirstClassFunctions(t *testing.T) {
 		{
 			input: `
         let returnsOneReturner = fn() {
-            let returnsOne = fn() { 1; };
+            let returnsOne = fn() { return 1; };
             returnsOne;
         };
         returnsOneReturner()();
@@ -444,32 +449,32 @@ func TestFirstClassFunctions(t *testing.T) {
 
 func TestCallingFunctionsWithBindings(t *testing.T) {
 	tests := []vmTestCase{
-		//{
-		//	input: `
-		//let one = fn() { let one = 1; one };
-		//one();
-		//`,
-		//	expected: 1,
-		//},
 		{
 			input: `
-        let oneAndTwo = fn() { let one = 1; let two = 2; one + two; };
+		let one = fn() { let one = 1; return one };
+		one();
+		`,
+			expected: 1,
+		},
+		{
+			input: `
+        let oneAndTwo = fn() { let one = 1; let two = 2; return one + two; };
         oneAndTwo();
         `,
 			expected: 3,
 		},
 		{
 			input: `
-        let oneAndTwo = fn() { let one = 1; let two = 2; one + two; };
+        let oneAndTwo = fn() { let one = 1; let two = 2; return one + two; };
-        let threeAndFour = fn() { let three = 3; let four = 4; three + four; };
+        let threeAndFour = fn() { let three = 3; let four = 4; return three + four; };
         oneAndTwo() + threeAndFour();
         `,
 			expected: 10,
 		},
 		{
 			input: `
-        let firstFoobar = fn() { let foobar = 50; foobar; };
+        let firstFoobar = fn() { let foobar = 50; return foobar; };
-        let secondFoobar = fn() { let foobar = 100; foobar; };
+        let secondFoobar = fn() { let foobar = 100; return foobar; };
         firstFoobar() + secondFoobar();
         `,
 			expected: 150,
@@ -479,11 +484,11 @@ func TestCallingFunctionsWithBindings(t *testing.T) {
         let globalSeed = 50;
         let minusOne = fn() {
             let num = 1;
-            globalSeed - num;
+            return globalSeed - num;
         }
         let minusTwo = fn() {
             let num = 2;
-            globalSeed - num;
+            return globalSeed - num;
         }
         minusOne() + minusTwo();
         `,
@@ -498,14 +503,14 @@ func TestCallingFunctionsWithArgumentsAndBindings(t *testing.T) {
 	tests := []vmTestCase{
 		{
 			input: `
-        let identity = fn(a) { a; };
+        let identity = fn(a) { return a; };
         identity(4);
         `,
 			expected: 4,
 		},
 		{
 			input: `
-        let sum = fn(a, b) { a + b; };
+        let sum = fn(a, b) { return a + b; };
         sum(1, 2);
         `,
 			expected: 3,
@@ -514,7 +519,7 @@ func TestCallingFunctionsWithArgumentsAndBindings(t *testing.T) {
 			input: `
         let sum = fn(a, b) {
             let c = a + b;
-            c;
+            return c;
         };
         sum(1, 2);
         `,
@@ -524,7 +529,7 @@ func TestCallingFunctionsWithArgumentsAndBindings(t *testing.T) {
 			input: `
         let sum = fn(a, b) {
             let c = a + b;
-            c;
+            return c;
         };
         sum(1, 2) + sum(3, 4);`,
 			expected: 10,
@@ -533,10 +538,10 @@ func TestCallingFunctionsWithArgumentsAndBindings(t *testing.T) {
 			input: `
         let sum = fn(a, b) {
             let c = a + b;
-            c;
+            return c;
         };
         let outer = fn() {
-            sum(1, 2) + sum(3, 4);
+            return sum(1, 2) + sum(3, 4);
         };
         outer();
         `,
@@ -548,11 +553,11 @@ func TestCallingFunctionsWithArgumentsAndBindings(t *testing.T) {
 
         let sum = fn(a, b) {
             let c = a + b;
-            c + globalNum;
+            return c + globalNum;
         };
 
         let outer = fn() {
-            sum(1, 2) + sum(3, 4) + globalNum;
+            return sum(1, 2) + sum(3, 4) + globalNum;
         };
 
         outer() + globalNum;
@@ -567,15 +572,15 @@ func TestCallingFunctionsWithArgumentsAndBindings(t *testing.T) {
 func TestCallingFunctionsWithWrongArguments(t *testing.T) {
 	tests := []vmTestCase{
 		{
-			input:    `fn() { 1; }(1);`,
+			input:    `fn() { return 1; }(1);`,
 			expected: `wrong number of arguments: want=0, got=1`,
 		},
 		{
-			input:    `fn(a) { a; }();`,
+			input:    `fn(a) { return a; }();`,
 			expected: `wrong number of arguments: want=1, got=0`,
 		},
 		{
-			input:    `fn(a, b) { a + b; }(1);`,
+			input:    `fn(a, b) { return a + b; }(1);`,
 			expected: `wrong number of arguments: want=2, got=1`,
 		},
 	}
@@ -658,7 +663,7 @@ func TestClosures(t *testing.T) {
 		{
 			input: `
         let newClosure = fn(a) {
-            fn() { a; };
+            fn() { return a; };
         };
         let closure = newClosure(99);
         closure();
@@ -668,7 +673,7 @@ func TestClosures(t *testing.T) {
 		{
 			input: `
         let newAdder = fn(a, b) {
-            fn(c) { a + b + c };
+            fn(c) { return a + b + c };
         };
         let adder = newAdder(1, 2);
         adder(8);
@@ -679,7 +684,7 @@ func TestClosures(t *testing.T) {
 			input: `
         let newAdder = fn(a, b) {
             let c = a + b;
-            fn(d) { c + d };
+            fn(d) { return c + d };
         };
         let adder = newAdder(1, 2);
         adder(8);
@@ -690,9 +695,9 @@ func TestClosures(t *testing.T) {
 			input: `
         let newAdderOuter = fn(a, b) {
             let c = a + b;
-            fn(d) {
+            return fn(d) {
                 let e = d + c;
-                fn(f) { e + f; };
+                return fn(f) { return e + f; };
             };
         };
         let newAdderInner = newAdderOuter(1, 2)
@@ -705,8 +710,8 @@ func TestClosures(t *testing.T) {
 			input: `
         let a = 1;
         let newAdderOuter = fn(b) {
-            fn(c) {
+            return fn(c) {
-                fn(d) { a + b + c + d };
+                return fn(d) { return a + b + c + d };
             };
         };
         let newAdderInner = newAdderOuter(2)
@@ -718,9 +723,9 @@ func TestClosures(t *testing.T) {
 		{
 			input: `
         let newClosure = fn(a, b) {
-            let one = fn() { a; };
+            let one = fn() { return a; };
-            let two = fn() { b; };
+            let two = fn() { return b; };
-            fn() { one() + two(); };
+            return fn() { return one() + two(); };
         };
         let closure = newClosure(9, 90);
         closure();
@@ -740,7 +745,7 @@ func TestRecursiveFunctions(t *testing.T) {
             if (x == 0) {
                 return 0;
             } else {
-                countDown(x - 1);
+                return countDown(x - 1);
             }
         };
         countDown(1);
@@ -753,11 +758,11 @@ func TestRecursiveFunctions(t *testing.T) {
             if (x == 0) {
                 return 0;
             } else {
-                countDown(x - 1);
+                return countDown(x - 1);
             }
         };
         let wrapper = fn() {
-            countDown(1);
+            return countDown(1);
         };
         wrapper();
         `,
@@ -770,10 +775,10 @@ func TestRecursiveFunctions(t *testing.T) {
                 if (x == 0) {
                     return 0;
                 } else {
-                    countDown(x - 1);
+                    return countDown(x - 1);
                 }
             };
-            countDown(1);
+            return countDown(1);
         };
         wrapper();
         `,
@@ -795,7 +800,7 @@ func TestRecursiveFibonacci(t *testing.T) {
                 if (x == 1) {
                     return 1;
                 } else {
-                    fibonacci(x - 1) + fibonacci(x - 2);
+                    return fibonacci(x - 1) + fibonacci(x - 2);
                 }
             }
         };