lots o fixes

internal/vm/vm.go

@@ -17,9 +17,11 @@ import (
 	"unicode"
 )
 
-const StackSize = 2048
-const GlobalsSize = 65536
-const MaxFrames = 1024
+const (
+	maxStackSize = 2048
+	maxFrames    = 1024
+	maxGlobals   = 65536
+)
 
 func isTruthy(obj object.Object) bool {
 	switch obj := obj.(type) {
@@ -36,7 +38,7 @@ func isTruthy(obj object.Object) bool {
 }
 
 // executeModule compiles the named module and returns a object.Module object
-func executeModule(name string, state *VMState) (object.Object, error) {
+func executeModule(name string, state *State) (object.Object, error) {
 	filename := utils.FindModule(name)
 	if filename == "" {
 		return nil, fmt.Errorf("ImportError: no module named '%s'", name)
@@ -73,21 +75,22 @@ func executeModule(name string, state *VMState) (object.Object, error) {
 	return state.ExportedHash(), nil
 }
 
-type VMState struct {
+// State is the state of the virtual machine.
+type State struct {
 	Constants []object.Object
 	Globals   []object.Object
 	Symbols   *compiler.SymbolTable
 }
 
-func NewVMState() *VMState {
+func NewState() *State {
 	symbolTable := compiler.NewSymbolTable()
 	for i, builtin := range builtins.BuiltinsIndex {
 		symbolTable.DefineBuiltin(i, builtin.Name)
 	}
 
-	return &VMState{
+	return &State{
 		Constants: []object.Object{},
-		Globals:   make([]object.Object, GlobalsSize),
+		Globals:   make([]object.Object, maxGlobals),
 		Symbols:   symbolTable,
 	}
 }
@@ -95,7 +98,7 @@ func NewVMState() *VMState {
 // exported binding in the vm state. That is every binding that starts with a
 // capital letter. This is used by the module import system to wrap up the
 // compiled and evaulated module into an object.
-func (s *VMState) ExportedHash() *object.Hash {
+func (s *State) ExportedHash() *object.Hash {
 	pairs := make(map[object.HashKey]object.HashPair)
 	for name, symbol := range s.Symbols.Store {
 		if unicode.IsUpper(rune(name[0])) {
@@ -113,7 +116,7 @@ type VM struct {
 	Debug bool
 	Trace bool
 
-	state *VMState
+	state *State
 
 	dir  string
 	file string
@@ -121,16 +124,16 @@ type VM struct {
 	stack []object.Object
 	sp    int // Always points to the next value. Top of stack is stack[sp-1]
 
-	frames []Frame
+	frames []frame
 	fp     int // Always points to the current frame. Current frame is frames[fp-1]
 }
 
-func (vm *VM) currentFrame() *Frame {
+func (vm *VM) currentFrame() *frame {
 	return &vm.frames[vm.fp-1]
 }
 
-func (vm *VM) pushFrame(f Frame) {
-	if vm.fp >= MaxFrames {
+func (vm *VM) pushFrame(f frame) {
+	if vm.fp >= maxFrames {
 		panic("frame overflow")
 	}
 
@@ -138,7 +141,7 @@ func (vm *VM) pushFrame(f Frame) {
 	vm.fp++
 }
 
-func (vm *VM) popFrame() Frame {
+func (vm *VM) popFrame() frame {
 	if vm.fp == 0 {
 		panic("fame underflow")
 	}
@@ -151,18 +154,18 @@ func (vm *VM) popFrame() Frame {
 func New(fn string, bytecode *compiler.Bytecode) *VM {
 	mainFn := object.CompiledFunction{Instructions: bytecode.Instructions}
 	mainClosure := object.Closure{Fn: &mainFn}
-	mainFrame := NewFrame(&mainClosure, 0)
+	mainFrame := newFrame(&mainClosure, 0)
 
-	frames := make([]Frame, MaxFrames)
+	frames := make([]frame, maxFrames)
 	frames[0] = mainFrame
 
-	state := NewVMState()
+	state := NewState()
 	state.Constants = bytecode.Constants
 
 	vm := &VM{
 		state: state,
 
-		stack: make([]object.Object, StackSize),
+		stack: make([]object.Object, maxStackSize),
 		sp:    0,
 
 		frames: frames,
@@ -174,12 +177,12 @@ func New(fn string, bytecode *compiler.Bytecode) *VM {
 	return vm
 }
 
-func NewWithState(fn string, bytecode *compiler.Bytecode, state *VMState) *VM {
+func NewWithState(fn string, bytecode *compiler.Bytecode, state *State) *VM {
 	mainFn := object.CompiledFunction{Instructions: bytecode.Instructions}
 	mainClosure := object.Closure{Fn: &mainFn}
-	mainFrame := NewFrame(&mainClosure, 0)
+	mainFrame := newFrame(&mainClosure, 0)
 
-	frames := make([]Frame, MaxFrames)
+	frames := make([]frame, maxFrames)
 	frames[0] = mainFrame
 
 	vm := &VM{
@@ -188,7 +191,7 @@ func NewWithState(fn string, bytecode *compiler.Bytecode, state *VMState) *VM {
 		frames: frames,
 		fp:     1,
 
-		stack: make([]object.Object, StackSize),
+		stack: make([]object.Object, maxStackSize),
 		sp:    0,
 	}
 
@@ -198,7 +201,7 @@ func NewWithState(fn string, bytecode *compiler.Bytecode, state *VMState) *VM {
 }
 
 func (vm *VM) push(o object.Object) error {
-	if vm.sp >= StackSize {
+	if vm.sp >= maxStackSize {
 		return fmt.Errorf("stack overflow")
 	}
 
@@ -712,7 +715,7 @@ func (vm *VM) callClosure(cl *object.Closure, numArgs int) error {
 		}
 	}
 
-	frame := NewFrame(cl, vm.sp-numArgs)
+	frame := newFrame(cl, vm.sp-numArgs)
 	vm.pushFrame(frame)
 	vm.sp = frame.basePointer + cl.Fn.NumLocals