further improvements

.gitignore

@@ -93,3 +93,4 @@ fabric.properties
 /.vscode
 /monkey
 /examples/fib
+vendor

.idea/.gitignore

@@ -1,8 +0,0 @@
-# Default ignored files
-/shelf/
-/workspace.xml
-# Editor-based HTTP Client requests
-/httpRequests/
-# Datasource local storage ignored files
-/dataSources/
-/dataSources.local.xml

.idea/git_toolbox_prj.xml

@@ -1,15 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<project version="4">
-  <component name="GitToolBoxProjectSettings">
-    <option name="commitMessageIssueKeyValidationOverride">
-      <BoolValueOverride>
-        <option name="enabled" value="true" />
-      </BoolValueOverride>
-    </option>
-    <option name="commitMessageValidationEnabledOverride">
-      <BoolValueOverride>
-        <option name="enabled" value="true" />
-      </BoolValueOverride>
-    </option>
-  </component>
-</project>

.idea/vcs.xml

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
   <component name="VcsDirectoryMappings">
-    <mapping directory="$PROJECT_DIR$" vcs="Git" />
+    <mapping directory="" vcs="Git" />
   </component>
 </project>

Benchmark.md

@@ -1,7 +1,7 @@
 | Command | Mean [ms] | Min [ms] | Max [ms] | Relative |
 |:---|---:|---:|---:|---:|
-| `c` | 36.7 ± 0.6 | 36.0 | 37.8 | 1.00 |
+| `c` | 37.4 ± 1.1 | 36.2 | 39.4 | 1.00 |
-| `go` | 230.2 ± 14.0 | 206.2 | 252.9 | 6.28 ± 0.40 |
+| `go` | 168.5 ± 27.2 | 120.2 | 202.6 | 4.51 ± 0.74 |
-| `python` | 1366.9 ± 30.8 | 1330.9 | 1411.3 | 37.27 ± 1.06 |
+| `python` | 1346.8 ± 8.2 | 1335.7 | 1361.6 | 36.05 ± 1.09 |
-| `tengo` | 1704.3 ± 16.0 | 1687.2 | 1739.3 | 46.47 ± 0.91 |
+| `tengo` | 1708.6 ± 15.9 | 1686.2 | 1731.4 | 45.74 ± 1.43 |
-| `monkey` | 3347.6 ± 22.3 | 3314.0 | 3396.0 | 91.27 ± 1.69 |
+| `monkey` | 2148.7 ± 6.6 | 2135.6 | 2157.0 | 57.52 ± 1.72 |

cmd/monkey/main.go

@@ -13,12 +13,14 @@ func main() {
 		version bool
 		simple  bool
 		debug   bool
+		trace   bool
 	)
 
 	flag.BoolVar(&compile, "c", false, "Compile a monkey file into a '.mc' bytecode file")
 	flag.BoolVar(&simple, "s", false, "Use simple REPL instead of opening a terminal")
 	flag.BoolVar(&version, "v", false, "Print Monkey version information")
-	flag.BoolVar(&debug, "d", false, "Enable debug mode")
+	flag.BoolVar(&debug, "D", false, "Enable Compiler and VM debugging")
+	flag.BoolVar(&trace, "T", false, "Enable VM tracing")
 	flag.Parse()
 
 	switch {
@@ -29,12 +31,12 @@ func main() {
 		monkey.PrintVersionInfo(os.Stdout)
 
 	case flag.NArg() > 0:
-		monkey.ExecFileVM(flag.Arg(0), flag.Args()[1:], debug)
+		monkey.ExecFileVM(flag.Arg(0), flag.Args()[1:], debug, trace)
 
 	case simple:
-		monkey.SimpleVmREPL(flag.Args(), debug)
+		monkey.SimpleVmREPL(flag.Args(), debug, trace)
 
 	default:
-		monkey.VmREPL(flag.Args(), debug)
+		monkey.VmREPL(flag.Args(), debug, trace)
 	}
 }

compare.sh

@@ -0,0 +1,24 @@
+#!/usr/bin/env bash
+
+if [ $# -ne 1 ]; then
+  echo "Usage: $(basename "$0") <branch>"
+  exit 1
+fi
+
+compareWith="$1"
+currentBranch="$(git branch --show-current)"
+
+if [ -n "$(git status --porcelain)" ]; then
+  echo "$currentBranch is not clean, please stash or commit your changes!"
+  exit 1
+fi
+
+hyperfine \
+  -w 5 \
+	-c "git checkout $currentBranch" \
+  -p "make build" \
+  -p "git checkout $compareWith; make build" \
+  -n "$currentBranch" \
+  -n "$compareWith" \
+  './monkey examples/fib.monkey' \
+  './monkey examples/fib.monkey'

go.mod

@@ -3,7 +3,6 @@ module monkey
 go 1.21
 
 require (
-	github.com/pkg/profile v1.7.0
 	github.com/stretchr/testify v1.8.4
 	github.com/tebeka/atexit v0.3.0
 	golang.org/x/term v0.18.0

go.sum

@@ -1,33 +1,20 @@
-github.com/chzyer/logex v1.1.10/go.mod h1:+Ywpsq7O8HXn0nuIou7OrIPyXbp3wmkHB+jjWRnGsAI=
-github.com/chzyer/readline v0.0.0-20180603132655-2972be24d48e/go.mod h1:nSuG5e5PlCu98SY8svDHJxuZscDgtXS6KTTbou5AhLI=
-github.com/chzyer/test v0.0.0-20180213035817-a1ea475d72b1/go.mod h1:Q3SI9o4m/ZMnBNeIyt5eFwwo7qiLfzFZmjNmxjkiQlU=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
-github.com/felixge/fgprof v0.9.3/go.mod h1:RdbpDgzqYVh/T9fPELJyV7EYJuHB55UTEULNun8eiPw=
-github.com/google/pprof v0.0.0-20211214055906-6f57359322fd/go.mod h1:KgnwoLYCZ8IQu3XUZ8Nc/bM9CCZFOyjUNOSygVozoDg=
-github.com/ianlancetaylor/demangle v0.0.0-20210905161508-09a460cdf81d/go.mod h1:aYm2/VgdVmcIU8iMfdMvDMsRAQjcfZSKFby6HOFvi/w=
-github.com/pkg/profile v1.7.0/go.mod h1:8Uer0jas47ZQMJ7VD+OHknK4YDY07LPUC6dEvqDjvNo=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
-github.com/stretchr/objx v0.4.0/go.mod h1:YvHI0jy2hoMjB+UWwv71VJQ9isScKT/TqJzVSSt89Yw=
 github.com/stretchr/testify v1.5.1/go.mod h1:5W2xD1RspED5o8YsWQXVCued0rvSQ+mT+I5cxcmMvtA=
-github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
-github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
 github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=
 github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
 github.com/tebeka/atexit v0.3.0 h1:jleL99H7Ywt80oJKR+VWmJNnezcCOG0CuzcN3CIpsdI=
 github.com/tebeka/atexit v0.3.0/go.mod h1:WJmSUSmMT7WoR7etUOaGBVXk+f5/ZJ+67qwuedq7Fbs=
-golang.org/x/sys v0.0.0-20211007075335-d3039528d8ac/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.18.0 h1:DBdB3niSjOA/O0blCZBqDefyWNYveAYMNF1Wum0DYQ4=
 golang.org/x/sys v0.18.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
-golang.org/x/term v0.15.0 h1:y/Oo/a/q3IXu26lQgl04j/gjuBDOBlx7X6Om1j2CPW4=
-golang.org/x/term v0.15.0/go.mod h1:BDl952bC7+uMoWR75FIrCDx79TPU9oHkTZ9yRbYOrX0=
 golang.org/x/term v0.18.0 h1:FcHjZXDMxI8mM3nwhX9HlKop4C0YQvCVCdwYl2wOtE8=
 golang.org/x/term v0.18.0/go.mod h1:ILwASektA3OnRv7amZ1xhE/KTR+u50pbXfZ03+6Nx58=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
-gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

internal/builtins/bind.go

@@ -50,5 +50,5 @@ func Bind(args ...object.Object) object.Object {
 		return newError("SocketError: %s", err)
 	}
 
-	return object.Null{}
+	return object.NULL
 }

internal/builtins/builtins.go

@@ -7,7 +7,7 @@ import (
 )
 
 // Builtins ...
-var Builtins = map[string]*object.Builtin{
+var Builtins = map[string]object.Builtin{
 	"len":       {Name: "len", Fn: Len},
 	"input":     {Name: "input", Fn: Input},
 	"print":     {Name: "print", Fn: Print},
@@ -58,7 +58,7 @@ var Builtins = map[string]*object.Builtin{
 }
 
 // BuiltinsIndex ...
-var BuiltinsIndex []*object.Builtin
+var BuiltinsIndex []object.Builtin
 
 func init() {
 	var keys []string

internal/builtins/close.go

@@ -23,5 +23,5 @@ func Close(args ...object.Object) object.Object {
 		return newError("IOError: %s", err)
 	}
 
-	return object.Null{}
+	return object.NULL
 }

internal/builtins/ffi.go

@@ -33,5 +33,5 @@ func FFI(args ...object.Object) object.Object {
 		return newError("error finding symbol: %s", err)
 	}
 
-	return &object.Builtin{Name: symbol, Fn: v.(object.BuiltinFunction)}
+	return object.Builtin{Name: symbol, Fn: v.(object.BuiltinFunction)}
 }

internal/builtins/id.go

@@ -30,11 +30,11 @@ func IdOf(args ...object.Object) object.Object {
 	} else if h, ok := arg.(*object.Hash); ok {
 		return object.String{Value: fmt.Sprintf("%p", h)}
 	} else if f, ok := arg.(*object.Function); ok {
-		return object.String{Value: fmt.Sprintf("%p", f)}
+		return object.String{Value: fmt.Sprintf("%p", &f)}
 	} else if c, ok := arg.(*object.Closure); ok {
-		return object.String{Value: fmt.Sprintf("%p", c)}
+		return object.String{Value: fmt.Sprintf("%p", &c)}
-	} else if b, ok := arg.(*object.Builtin); ok {
+	} else if b, ok := arg.(object.Builtin); ok {
-		return object.String{Value: fmt.Sprintf("%p", b)}
+		return object.String{Value: fmt.Sprintf("%p", &b)}
 	}
 	return nil
 }

internal/builtins/listen.go

@@ -23,5 +23,5 @@ func Listen(args ...object.Object) object.Object {
 		return newError("SocketError: %s", err)
 	}
 
-	return object.Null{}
+	return object.NULL
 }

internal/builtins/writefile.go

@@ -24,5 +24,5 @@ func WriteFile(args ...object.Object) object.Object {
 		return newError("IOError: error writing file %s: %s", filename, err)
 	}
 
-	return object.Null{}
+	return object.NULL
 }

internal/evaluator/evaluator.go

@@ -126,7 +126,7 @@ func Eval(node ast.Node, env *object.Environment) object.Object {
 	case *ast.FunctionLiteral:
 		params := node.Parameters
 		body := node.Body
-		return &object.Function{Parameters: params, Env: env, Body: body}
+		return object.Function{Parameters: params, Env: env, Body: body}
 
 	// Expressions
 	case *ast.IntegerLiteral:
@@ -560,12 +560,12 @@ func evalExpressions(exps []ast.Expression, env *object.Environment) []object.Ob
 func applyFunction(fn object.Object, args []object.Object) object.Object {
 	switch fn := fn.(type) {
 
-	case *object.Function:
+	case object.Function:
 		extendedEnv := extendFunctionEnv(fn, args)
 		evaluated := Eval(fn.Body, extendedEnv)
 		return unwrapReturnValue(evaluated)
 
-	case *object.Builtin:
+	case object.Builtin:
 		if result := fn.Fn(args...); result != nil {
 			return result
 		}
@@ -577,7 +577,7 @@ func applyFunction(fn object.Object, args []object.Object) object.Object {
 	}
 }
 
-func extendFunctionEnv(fn *object.Function, args []object.Object) *object.Environment {
+func extendFunctionEnv(fn object.Function, args []object.Object) *object.Environment {
 	env := object.NewEnclosedEnvironment(fn.Env)
 
 	for paramIdx, param := range fn.Parameters {

internal/evaluator/evaluator_test.go

@@ -354,7 +354,7 @@ func TestFunctionObject(t *testing.T) {
 	input := "fn(x) { x + 2; };"
 
 	evaluated := testEval(input)
-	fn, ok := evaluated.(*object.Function)
+	fn, ok := evaluated.(object.Function)
 	if !ok {
 		t.Fatalf("object is not Function. got=%T (%+v)", evaluated, evaluated)
 	}

internal/object/bool.go

@@ -4,10 +4,22 @@ import (
 	"fmt"
 )
 
+var (
+	TRUE  = Boolean{Value: true}
+	FALSE = Boolean{Value: false}
+)
+
 type Boolean struct {
 	Value bool
 }
 
+func NewBoolean(value bool) Boolean {
+	if value {
+		return TRUE
+	}
+	return FALSE
+}
+
 func (b Boolean) Bool() bool {
 	return b.Value
 }

internal/object/builtin.go

@@ -7,18 +7,18 @@ type Builtin struct {
 	Fn   BuiltinFunction
 }
 
-func (b *Builtin) Bool() bool {
+func (b Builtin) Bool() bool {
 	return true
 }
 
-func (b *Builtin) Type() Type {
+func (b Builtin) Type() Type {
 	return BuiltinType
 }
 
-func (b *Builtin) Inspect() string {
+func (b Builtin) Inspect() string {
 	return fmt.Sprintf("<built-in function %s>", b.Name)
 }
 
-func (b *Builtin) String() string {
+func (b Builtin) String() string {
 	return b.Inspect()
 }

internal/object/int.go

@@ -27,17 +27,21 @@ func (i Integer) String() string {
 }
 
 func (i Integer) Add(other Object) (Object, error) {
-	if !AssertTypes(other, IntegerType) {
+	switch obj := other.(type) {
+	case Integer:
+		return Integer{i.Value + obj.Value}, nil
+	default:
 		return nil, NewBinaryOpError(i, other, "+")
 	}
-	return Integer{i.Value + other.(Integer).Value}, nil
 }
 
 func (i Integer) Sub(other Object) (Object, error) {
-	if !AssertTypes(other, IntegerType) {
+	switch obj := other.(type) {
+	case Integer:
+		return Integer{i.Value - obj.Value}, nil
+	default:
 		return nil, NewBinaryOpError(i, other, "-")
 	}
-	return Integer{i.Value - other.(Integer).Value}, nil
 }
 
 func (i Integer) Mul(other Object) (Object, error) {
@@ -115,15 +119,16 @@ func (i Integer) Negate() Object {
 }
 
 func (i Integer) Compare(other Object) int {
-	if obj, ok := other.(Integer); ok {
+	switch obj := other.(type) {
-		switch {
+	case Integer:
-		case i.Value < obj.Value:
+		if i.Value < obj.Value {
 			return -1
-		case i.Value > obj.Value:
-			return 1
-		default:
-			return 0
 		}
+		if i.Value > obj.Value {
+			return 1
+		}
+		return 0
+	default:
+		return -1
 	}
-	return -1
 }

internal/object/null.go

@@ -1,5 +1,7 @@
 package object
 
+var NULL = Null{}
+
 type Null struct{}
 
 func (n Null) Bool() bool {

internal/vm/vm.go

@@ -12,6 +12,7 @@ import (
 	"monkey/internal/utils"
 	"os"
 	"path/filepath"
+	"sort"
 	"time"
 	"unicode"
 )
@@ -20,10 +21,6 @@ const StackSize = 2048
 const GlobalsSize = 65536
 const MaxFrames = 1024
 
-var Null = object.Null{}
-var True = object.Boolean{Value: true}
-var False = object.Boolean{Value: false}
-
 func isTruthy(obj object.Object) bool {
 	switch obj := obj.(type) {
 
@@ -114,6 +111,7 @@ func (s *VMState) ExportedHash() *object.Hash {
 
 type VM struct {
 	Debug bool
+	Trace bool
 
 	state *VMState
 
@@ -143,9 +141,9 @@ func (vm *VM) popFrame() Frame {
 
 // New constructs a new monkey-lang bytecode virtual machine
 func New(fn string, bytecode *compiler.Bytecode) *VM {
-	mainFn := &object.CompiledFunction{Instructions: bytecode.Instructions}
+	mainFn := object.CompiledFunction{Instructions: bytecode.Instructions}
-	mainClosure := &object.Closure{Fn: mainFn}
+	mainClosure := object.Closure{Fn: &mainFn}
-	mainFrame := NewFrame(mainClosure, 0)
+	mainFrame := NewFrame(&mainClosure, 0)
 
 	frames := make([]Frame, MaxFrames)
 	frames[0] = mainFrame
@@ -169,9 +167,9 @@ func New(fn string, bytecode *compiler.Bytecode) *VM {
 }
 
 func NewWithState(fn string, bytecode *compiler.Bytecode, state *VMState) *VM {
-	mainFn := &object.CompiledFunction{Instructions: bytecode.Instructions}
+	mainFn := object.CompiledFunction{Instructions: bytecode.Instructions}
-	mainClosure := &object.Closure{Fn: mainFn}
+	mainClosure := object.Closure{Fn: &mainFn}
-	mainFrame := NewFrame(mainClosure, 0)
+	mainFrame := NewFrame(&mainClosure, 0)
 
 	frames := make([]Frame, MaxFrames)
 	frames[0] = mainFrame
@@ -222,13 +220,13 @@ func (vm *VM) executeConstant() error {
 func (vm *VM) executeAssignGlobal() error {
 	globalIndex := vm.currentFrame().ReadUint16()
 	vm.state.Globals[globalIndex] = vm.pop()
-	return vm.push(Null)
+	return vm.push(object.NULL)
 }
 
 func (vm *VM) executeAssignLocal() error {
 	localIndex := vm.currentFrame().ReadUint8()
 	vm.stack[vm.currentFrame().basePointer+int(localIndex)] = vm.pop()
-	return vm.push(Null)
+	return vm.push(object.NULL)
 }
 
 func (vm *VM) executeSetGlobal() error {
@@ -241,7 +239,7 @@ func (vm *VM) executeSetGlobal() error {
 		vm.state.Globals[globalIndex] = ref
 	}
 
-	return vm.push(Null)
+	return vm.push(object.NULL)
 }
 
 func (vm *VM) executeGetGlobal() error {
@@ -259,7 +257,7 @@ func (vm *VM) executeSetLocal() error {
 		vm.stack[vm.currentFrame().basePointer+int(localIndex)] = ref
 	}
 
-	return vm.push(Null)
+	return vm.push(object.NULL)
 }
 
 func (vm *VM) executeGetLocal() error {
@@ -283,15 +281,15 @@ func (vm *VM) executeCurrentClosure() error {
 }
 
 func (vm *VM) executeTrue() error {
-	return vm.push(True)
+	return vm.push(object.TRUE)
 }
 
 func (vm *VM) executeFalse() error {
-	return vm.push(False)
+	return vm.push(object.FALSE)
 }
 
 func (vm *VM) executeNull() error {
-	return vm.push(Null)
+	return vm.push(object.NULL)
 }
 
 func (vm *VM) buildHash(startIndex, endIndex int) (object.Object, error) {
@@ -547,9 +545,9 @@ func (vm *VM) executeEqual() error {
 	if obj, ok := left.(object.Comparable); ok {
 		val := obj.Compare(right)
 		if val == 0 {
-			return vm.push(True)
+			return vm.push(object.TRUE)
 		}
-		return vm.push(False)
+		return vm.push(object.FALSE)
 	}
 
 	return object.NewBinaryOpError(left, right, "==")
@@ -562,9 +560,9 @@ func (vm *VM) executeNotEqual() error {
 	if obj, ok := left.(object.Comparable); ok {
 		val := obj.Compare(right)
 		if val != 0 {
-			return vm.push(True)
+			return vm.push(object.TRUE)
 		}
-		return vm.push(False)
+		return vm.push(object.FALSE)
 	}
 
 	return object.NewBinaryOpError(left, right, "!=")
@@ -577,9 +575,9 @@ func (vm *VM) executeGreaterThan() error {
 	if obj, ok := left.(object.Comparable); ok {
 		val := obj.Compare(right)
 		if val == 1 {
-			return vm.push(True)
+			return vm.push(object.TRUE)
 		}
-		return vm.push(False)
+		return vm.push(object.FALSE)
 	}
 
 	return object.NewBinaryOpError(left, right, ">")
@@ -592,9 +590,9 @@ func (vm *VM) executeGreaterThanOrEqual() error {
 	if obj, ok := left.(object.Comparable); ok {
 		val := obj.Compare(right)
 		if val >= 0 {
-			return vm.push(True)
+			return vm.push(object.TRUE)
 		}
-		return vm.push(False)
+		return vm.push(object.FALSE)
 	}
 
 	return object.NewBinaryOpError(left, right, ">")
@@ -630,7 +628,7 @@ func (vm *VM) executeSetItem() error {
 		if err != nil {
 			return err
 		}
-		return vm.push(Null)
+		return vm.push(object.NULL)
 	}
 
 	return fmt.Errorf(
@@ -664,7 +662,7 @@ func (vm *VM) executeCall() error {
 	switch callee := callee.(type) {
 	case *object.Closure:
 		return vm.callClosure(callee, args)
-	case *object.Builtin:
+	case object.Builtin:
 		return vm.callBuiltin(callee, args)
 	default:
 		return fmt.Errorf(
@@ -727,7 +725,7 @@ func (vm *VM) callClosure(cl *object.Closure, numArgs int) error {
 	return nil
 }
 
-func (vm *VM) callBuiltin(builtin *object.Builtin, numArgs int) error {
+func (vm *VM) callBuiltin(builtin object.Builtin, numArgs int) error {
 	args := vm.stack[vm.sp-numArgs : vm.sp]
 
 	result := builtin.Fn(args...)
@@ -739,7 +737,7 @@ func (vm *VM) callBuiltin(builtin *object.Builtin, numArgs int) error {
 			return err
 		}
 	} else {
-		err := vm.push(Null)
+		err := vm.push(object.NULL)
 		if err != nil {
 			return err
 		}
@@ -761,8 +759,8 @@ func (vm *VM) pushClosure(constIndex, numFree int) error {
 	}
 	vm.sp = vm.sp - numFree
 
-	closure := &object.Closure{Fn: function, Free: free}
+	closure := object.Closure{Fn: function, Free: free}
-	return vm.push(closure)
+	return vm.push(&closure)
 }
 
 func (vm *VM) loadModule(name object.Object) error {
@@ -788,20 +786,38 @@ func (vm *VM) LastPoppedStackElem() object.Object {
 }
 
 func (vm *VM) Run() (err error) {
-	var n int
+	var (
+		op          code.Opcode
+		opcodeFreqs = make(map[code.Opcode]int)
+	)
 
 	if vm.Debug {
 		start := time.Now()
 		defer func() {
-			log.Printf("%d instructions executeuted in %s", n, time.Now().Sub(start))
+			total := 0
+			opcodes := make([]code.Opcode, 0, len(opcodeFreqs))
+
+			for opcode := range opcodeFreqs {
+				opcodes = append(opcodes, opcode)
+			}
+
+			sort.SliceStable(opcodes, func(i, j int) bool {
+				return opcodeFreqs[opcodes[i]] > opcodeFreqs[opcodes[j]]
+			})
+
+			log.Printf("%d instructions executed in %s", total, time.Now().Sub(start))
+			log.Print("Top 10 instructions:")
+			for _, opcode := range opcodes[:10] {
+				log.Printf("%10d %s", opcodeFreqs[opcode], opcode)
+			}
 		}()
 	}
 
 	for err == nil {
-		op := vm.currentFrame().ReadNextOp()
+		op = vm.currentFrame().ReadNextOp()
 
 		if vm.Debug {
-			n++
+			opcodeFreqs[op]++
 			log.Printf(
 				"%-25s %-20s\n",
 				fmt.Sprintf("%04d %s", vm.currentFrame().ip, op),
@@ -949,7 +965,7 @@ func (vm *VM) Run() (err error) {
 			err = fmt.Errorf("unhandled opcode: %s", op)
 		}
 
-		if vm.Debug {
+		if vm.Trace {
 			log.Printf(
 				"%-25s [ip=%02d fp=%02d, sp=%02d]",
 				"", vm.currentFrame().ip, vm.fp-1, vm.sp,

internal/vm/vm_test.go

@@ -130,7 +130,7 @@ func testExpectedObject(t *testing.T, expected interface{}, actual object.Object
 		}
 
 	case object.Null:
-		if actual != Null {
+		if actual != object.NULL {
 			t.Errorf("object is not Null: %T (%+v)", actual, actual)
 		}
 
@@ -302,14 +302,14 @@ func TestConditionals(t *testing.T) {
 		{"if (1 < 2) { 10 }", 10},
 		{"if (1 < 2) { 10 } else { 20 }", 10},
 		{"if (1 > 2) { 10 } else { 20 }", 20},
-		{"if (1 > 2) { 10 }", Null},
+		{"if (1 > 2) { 10 }", object.NULL},
-		{"if (false) { 10 }", Null},
+		{"if (false) { 10 }", object.NULL},
 		{"if ((if (false) { 10 })) { 10 } else { 20 }", 20},
-		{"if (true) { a := 5; }", Null},
+		{"if (true) { a := 5; }", object.NULL},
-		{"if (true) { 10; a := 5; }", Null},
+		{"if (true) { 10; a := 5; }", object.NULL},
-		{"if (false) { 10 } else { b := 5; }", Null},
+		{"if (false) { 10 } else { b := 5; }", object.NULL},
-		{"if (false) { 10 } else { 10; b := 5; }", Null},
+		{"if (false) { 10 } else { 10; b := 5; }", object.NULL},
-		{"if (true) { a := 5; } else { 10 }", Null},
+		{"if (true) { a := 5; } else { 10 }", object.NULL},
 		{"x := 0; if (true) { x = 1; }; if (false) { x = 2; }; x", 1},
 		{"if (1 < 2) { 10 } else if (1 == 2) { 20 }", 10},
 		{"if (1 > 2) { 10 } else if (1 == 2) { 20 } else { 30 }", 30},
@@ -430,13 +430,13 @@ func TestIndexExpressions(t *testing.T) {
 		{"[1, 2, 3][1]", 2},
 		{"[1, 2, 3][0 + 2]", 3},
 		{"[[1, 1, 1]][0][0]", 1},
-		{"[][0]", Null},
+		{"[][0]", object.NULL},
-		{"[1, 2, 3][99]", Null},
+		{"[1, 2, 3][99]", object.NULL},
-		{"[1][-1]", Null},
+		{"[1][-1]", object.NULL},
 		{"{1: 1, 2: 2}[1]", 1},
 		{"{1: 1, 2: 2}[2]", 2},
-		{"{1: 1}[0]", Null},
+		{"{1: 1}[0]", object.NULL},
-		{"{}[0]", Null},
+		{"{}[0]", object.NULL},
 		{`"abc"[0]`, "a"},
 		{`"abc"[1]`, "b"},
 		{`"abc"[2]`, "c"},
@@ -506,7 +506,7 @@ func TestFunctionsWithoutReturnValue(t *testing.T) {
         noReturn := fn() { };
         noReturn();
         `,
-			expected: Null,
+			expected: object.NULL,
 		},
 		{
 			input: `
@@ -515,7 +515,7 @@ func TestFunctionsWithoutReturnValue(t *testing.T) {
         noReturn();
         noReturnTwo();
         `,
-			expected: Null,
+			expected: object.NULL,
 		},
 	}
 
@@ -724,16 +724,16 @@ func TestBuiltinFunctions(t *testing.T) {
 		},
 		{`len([1, 2, 3])`, 3},
 		{`len([])`, 0},
-		{`print("hello", "world!")`, Null},
+		{`print("hello", "world!")`, object.NULL},
 		{`first([1, 2, 3])`, 1},
-		{`first([])`, Null},
+		{`first([])`, object.NULL},
 		{`first(1)`,
 			&object.Error{
 				Message: "TypeError: first() expected argument #1 to be `array` got `int`",
 			},
 		},
 		{`last([1, 2, 3])`, 3},
-		{`last([])`, Null},
+		{`last([])`, object.NULL},
 		{`last(1)`,
 			&object.Error{
 				Message: "TypeError: last() expected argument #1 to be `array` got `int`",

monkey.go

@@ -71,7 +71,7 @@ func compile(path string, debug bool) (bc *compiler.Bytecode, err error) {
 	return c.Bytecode(), nil
 }
 
-func ExecFileVM(f string, args []string, debug bool) (err error) {
+func ExecFileVM(f string, args []string, debug, trace bool) (err error) {
 	var bytecode *compiler.Bytecode
 
 	object.Args = args
@@ -89,6 +89,7 @@ func ExecFileVM(f string, args []string, debug bool) (err error) {
 
 	mvm := vm.New(f, bytecode)
 	mvm.Debug = debug
+	mvm.Trace = trace
 	if err = mvm.Run(); err != nil {
 		fmt.Println(err)
 		return

repl.go

@@ -20,7 +20,7 @@ import (
 // Package repl implements the Read-Eval-Print-Loop or interactive console
 // by lexing, parsing and evaluating the input in the interpreter
 
-func VmREPL(args []string, debug bool) error {
+func VmREPL(args []string, debug, trace bool) error {
 	var state = vm.NewVMState()
 
 	object.Args = args
@@ -73,6 +73,8 @@ func VmREPL(args []string, debug bool) error {
 
 		mvm := vm.NewWithState("<stdin>", c.Bytecode(), state)
 		mvm.Debug = debug
+		mvm.Trace = trace
+
 		if err := mvm.Run(); err != nil {
 			fmt.Fprintf(t, "runtime error: %v\n", err)
 			continue
@@ -129,7 +131,7 @@ func acceptUntil(t *term.Terminal, start, end string) (string, error) {
 	return buf.String(), nil
 }
 
-func SimpleVmREPL(args []string, debug bool) {
+func SimpleVmREPL(args []string, debug, trace bool) {
 	var (
 		state  = vm.NewVMState()
 		reader = bufio.NewReader(os.Stdin)
@@ -171,6 +173,8 @@ func SimpleVmREPL(args []string, debug bool) {
 
 		mvm := vm.NewWithState("<stdin>", c.Bytecode(), state)
 		mvm.Debug = debug
+		mvm.Trace = trace
+
 		if err := mvm.Run(); err != nil {
 			fmt.Printf("runtime error: %v\n", err)
 			continue