restructure project

.gitignore

@@ -81,11 +81,13 @@ fabric.properties
 *-e
 *.so
 *.bak
-*.txt
+*.out
 *.swo
 *.swn
-.DS_Store
+*.prof
+
+**/.DS_Store
 
 /dist
 /.vscode
-/monkey-lang
+/monkey

cmd/monkey/main.go

@@ -3,18 +3,21 @@ package main
 import (
 	"flag"
 	"fmt"
-	"github.com/pkg/profile"
 	"io"
 	"log"
-	"monkey/compiler"
-	"monkey/lexer"
-	"monkey/object"
-	"monkey/parser"
-	"monkey/repl"
 	"os"
 	"os/user"
 	"path"
 	"strings"
+
+	"github.com/pkg/profile"
+
+	"monkey/internal"
+	"monkey/internal/compiler"
+	"monkey/internal/lexer"
+	"monkey/internal/object"
+	"monkey/internal/parser"
+	"monkey/internal/repl"
 )
 
 var (
@@ -66,7 +69,7 @@ func main() {
 	flag.Parse()
 
 	if version {
-		fmt.Printf("%s %s", path.Base(os.Args[0]), FullVersion())
+		fmt.Printf("%s %s", path.Base(os.Args[0]), internal.FullVersion())
 		os.Exit(0)
 	}
 

examples/fib.monkey

@@ -5,4 +5,10 @@ fib := fn(x) {
   return fib(x-1) + fib(x-2)
 }
 
-print(fib(35))
+N := 35
+
+if (len(args()) == 1) {
+  N = int(args()[0])
+}
+
+print(fib(N))

internal/ast/ast.go

@@ -3,7 +3,7 @@ package ast
 import (
 	"bytes"
 	"fmt"
-	"monkey/token"
+	"monkey/internal/token"
 	"strings"
 )
 

internal/ast/ast_test.go

@@ -2,7 +2,7 @@ package ast
 
 import (
 	"github.com/stretchr/testify/assert"
-	"monkey/token"
+	"monkey/internal/token"
 	"testing"
 )
 

internal/builtins/abs.go

@@ -1,8 +1,8 @@
 package builtins
 
 import (
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 )
 
 // Abs  ...

internal/builtins/accept.go

@@ -1,8 +1,8 @@
 package builtins
 
 import (
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 	"syscall"
 )
 

internal/builtins/args.go

@@ -1,8 +1,8 @@
 package builtins
 
 import (
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 )
 
 // Args ...

internal/builtins/assert.go

@@ -1,12 +1,9 @@
 package builtins
 
-import (
-	"monkey/object"
-	"monkey/typing"
-)
-
 import (
 	"fmt"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 	"os"
 )
 

internal/builtins/bin.go

@@ -2,8 +2,8 @@ package builtins
 
 import (
 	"fmt"
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 	"strconv"
 )
 

internal/builtins/bind.go

@@ -1,8 +1,8 @@
 package builtins
 
 import (
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 	"syscall"
 )
 

internal/builtins/bool.go

@@ -1,8 +1,8 @@
 package builtins
 
 import (
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 )
 
 // Bool ...

internal/builtins/builtins.go

@@ -2,7 +2,7 @@ package builtins
 
 import (
 	"fmt"
-	"monkey/object"
+	"monkey/internal/object"
 	"sort"
 )
 

internal/builtins/chr.go

@@ -2,8 +2,8 @@ package builtins
 
 import (
 	"fmt"
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 )
 
 // Chr ...

internal/builtins/close.go

@@ -1,8 +1,8 @@
 package builtins
 
 import (
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 	"syscall"
 )
 

internal/builtins/connect.go

@@ -1,8 +1,8 @@
 package builtins
 
 import (
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 	"syscall"
 )
 

internal/builtins/divmod.go

@@ -1,8 +1,8 @@
 package builtins
 
 import (
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 )
 
 // Divmod ...

internal/builtins/exit.go

@@ -1,8 +1,8 @@
 package builtins
 
 import (
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 )
 
 // Exit ...

internal/builtins/ffi.go

@@ -1,8 +1,8 @@
 package builtins
 
 import (
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 )
 
 import (

internal/builtins/find.go

@@ -1,8 +1,8 @@
 package builtins
 
 import (
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 	"sort"
 )
 

internal/builtins/first.go

@@ -1,8 +1,8 @@
 package builtins
 
 import (
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 )
 
 // First ...

internal/builtins/hash.go

@@ -1,8 +1,8 @@
 package builtins
 
 import (
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 )
 
 // HashOf ...

internal/builtins/hex.go

@@ -2,8 +2,8 @@ package builtins
 
 import (
 	"fmt"
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 	"strconv"
 )
 

internal/builtins/id.go

@@ -2,8 +2,8 @@ package builtins
 
 import (
 	"fmt"
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 )
 
 // IdOf ...

internal/builtins/input.go

@@ -1,14 +1,11 @@
 package builtins
 
-import (
-	"monkey/object"
-	"monkey/typing"
-)
-
 import (
 	"bufio"
 	"fmt"
 	"io"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 	"os"
 )
 

internal/builtins/int.go

@@ -1,12 +1,11 @@
 package builtins
 
 import (
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
+	"strconv"
 )
 
-import "strconv"
-
 // Int ...
 func Int(args ...object.Object) object.Object {
 	if err := typing.Check(

internal/builtins/join.go

@@ -1,11 +1,8 @@
 package builtins
 
 import (
-	"monkey/object"
-	"monkey/typing"
-)
-
-import (
+	"monkey/internal/object"
+	"monkey/internal/typing"
 	"strings"
 )
 

internal/builtins/last.go

@@ -1,8 +1,8 @@
 package builtins
 
 import (
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 )
 
 // Last ...

internal/builtins/len.go

@@ -1,8 +1,8 @@
 package builtins
 
 import (
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 )
 
 // Len ...

internal/builtins/listen.go

@@ -1,8 +1,8 @@
 package builtins
 
 import (
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 	"syscall"
 )
 

internal/builtins/lower.go

@@ -1,12 +1,11 @@
 package builtins
 
 import (
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
+	"strings"
 )
 
-import "strings"
-
 // Lower ...
 func Lower(args ...object.Object) object.Object {
 	if err := typing.Check(

internal/builtins/max.go

@@ -1,8 +1,8 @@
 package builtins
 
 import (
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 	"sort"
 )
 

internal/builtins/min.go

@@ -1,8 +1,8 @@
 package builtins
 
 import (
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 	"sort"
 )
 

internal/builtins/oct.go

@@ -2,8 +2,8 @@ package builtins
 
 import (
 	"fmt"
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 	"strconv"
 )
 

internal/builtins/open.go

@@ -3,8 +3,8 @@ package builtins
 import (
 	"fmt"
 	"log"
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 	"os"
 	"syscall"
 )

internal/builtins/ord.go

@@ -1,8 +1,8 @@
 package builtins
 
 import (
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 )
 
 // Ord ...

internal/builtins/pop.go

@@ -1,8 +1,8 @@
 package builtins
 
 import (
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 )
 
 // Pop ...

internal/builtins/pow.go

@@ -1,8 +1,8 @@
 package builtins
 
 import (
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 )
 
 func pow(x, y int64) int64 {

internal/builtins/print.go

@@ -1,12 +1,11 @@
 package builtins
 
 import (
-	"monkey/object"
-	"monkey/typing"
+	"fmt"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 )
 
-import "fmt"
-
 // Print ...
 func Print(args ...object.Object) object.Object {
 	if err := typing.Check(

internal/builtins/push.go

@@ -1,8 +1,8 @@
 package builtins
 
 import (
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 )
 
 // Push ...

internal/builtins/read.go

@@ -1,8 +1,8 @@
 package builtins
 
 import (
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 	"syscall"
 )
 

internal/builtins/readfile.go

@@ -2,8 +2,8 @@ package builtins
 
 import (
 	"io/ioutil"
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 )
 
 // ReadFile ...

internal/builtins/rest.go

@@ -1,8 +1,8 @@
 package builtins
 
 import (
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 )
 
 // Rest ...

internal/builtins/reversed.go

@@ -1,8 +1,8 @@
 package builtins
 
 import (
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 )
 
 // Reversed ...

internal/builtins/seek.go

@@ -1,8 +1,8 @@
 package builtins
 
 import (
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 	"syscall"
 )
 

internal/builtins/socket.go

@@ -1,8 +1,8 @@
 package builtins
 
 import (
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 	"strings"
 	"syscall"
 )

internal/builtins/sorted.go

@@ -1,8 +1,8 @@
 package builtins
 
 import (
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 	"sort"
 )
 

internal/builtins/split.go

@@ -1,11 +1,8 @@
 package builtins
 
 import (
-	"monkey/object"
-	"monkey/typing"
-)
-
-import (
+	"monkey/internal/object"
+	"monkey/internal/typing"
 	"strings"
 )
 

internal/builtins/str.go

@@ -1,8 +1,8 @@
 package builtins
 
 import (
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 )
 
 // Str ...

internal/builtins/typeof.go

@@ -1,8 +1,8 @@
 package builtins
 
 import (
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 )
 
 // TypeOf ...

internal/builtins/upper.go

@@ -1,8 +1,8 @@
 package builtins
 
 import (
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 	"strings"
 )
 

internal/builtins/write.go

@@ -1,8 +1,8 @@
 package builtins
 
 import (
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 	"syscall"
 )
 

internal/builtins/writefile.go

@@ -2,8 +2,8 @@ package builtins
 
 import (
 	"io/ioutil"
-	"monkey/object"
-	"monkey/typing"
+	"monkey/internal/object"
+	"monkey/internal/typing"
 )
 
 // WriteFile ...

internal/compiler/compiler.go

@@ -3,10 +3,10 @@ package compiler
 import (
 	"fmt"
 	"log"
-	"monkey/ast"
-	"monkey/builtins"
-	"monkey/code"
-	"monkey/object"
+	"monkey/internal/ast"
+	"monkey/internal/builtins"
+	"monkey/internal/code"
+	"monkey/internal/object"
 	"sort"
 	"strings"
 )

internal/compiler/compiler_test.go

@@ -3,11 +3,11 @@ package compiler
 import (
 	"fmt"
 	"github.com/stretchr/testify/assert"
-	"monkey/ast"
-	"monkey/code"
-	"monkey/lexer"
-	"monkey/object"
-	"monkey/parser"
+	"monkey/internal/ast"
+	"monkey/internal/code"
+	"monkey/internal/lexer"
+	"monkey/internal/object"
+	"monkey/internal/parser"
 	"testing"
 )
 

internal/evaluator/evaluator.go

@@ -2,12 +2,12 @@ package evaluator
 
 import (
 	"fmt"
-	"monkey/ast"
-	"monkey/builtins"
-	"monkey/lexer"
-	"monkey/object"
-	"monkey/parser"
-	"monkey/utils"
+	"monkey/internal/ast"
+	"monkey/internal/builtins"
+	"monkey/internal/lexer"
+	"monkey/internal/object"
+	"monkey/internal/parser"
+	"monkey/internal/utils"
 	"os"
 	"strings"
 )

internal/evaluator/evaluator_test.go

@@ -3,10 +3,10 @@ package evaluator
 import (
 	"errors"
 	"github.com/stretchr/testify/assert"
-	"monkey/lexer"
-	"monkey/object"
-	"monkey/parser"
-	"monkey/utils"
+	"monkey/internal/lexer"
+	"monkey/internal/object"
+	"monkey/internal/parser"
+	"monkey/internal/utils"
 	"os"
 	"path"
 	"path/filepath"
@@ -862,9 +862,9 @@ func TestImportExpressions(t *testing.T) {
 		input    string
 		expected interface{}
 	}{
-		{`mod := import("../testdata/mod"); mod.A`, 5},
-		{`mod := import("../testdata/mod"); mod.Sum(2, 3)`, 5},
-		{`mod := import("../testdata/mod"); mod.a`, nil},
+		{`mod := import("../../testdata/mod"); mod.A`, 5},
+		{`mod := import("../../testdata/mod"); mod.Sum(2, 3)`, 5},
+		{`mod := import("../../testdata/mod"); mod.a`, nil},
 	}
 
 	for _, tt := range tests {
@@ -890,7 +890,7 @@ func TestImportSearchPaths(t *testing.T) {
 }
 
 func TestExamples(t *testing.T) {
-	matches, err := filepath.Glob("./examples/*.monkey")
+	matches, err := filepath.Glob("../../examples/*.monkey")
 	if err != nil {
 		t.Error(err)
 	}

internal/lexer/lexer.go

@@ -2,7 +2,7 @@ package lexer
 
 import (
 	"encoding/hex"
-	"monkey/token"
+	"monkey/internal/token"
 	"strings"
 )
 

internal/lexer/lexer_test.go

@@ -1,7 +1,7 @@
 package lexer
 
 import (
-	"monkey/token"
+	"monkey/internal/token"
 	"testing"
 )
 

internal/object/closure.go

@@ -2,7 +2,7 @@ package object
 
 import (
 	"fmt"
-	"monkey/code"
+	"monkey/internal/code"
 )
 
 type CompiledFunction struct {

internal/object/function.go

@@ -2,7 +2,7 @@ package object
 
 import (
 	"bytes"
-	"monkey/ast"
+	"monkey/internal/ast"
 	"strings"
 )
 

internal/parser/parser.go

@@ -2,9 +2,9 @@ package parser
 
 import (
 	"fmt"
-	"monkey/ast"
-	"monkey/lexer"
-	"monkey/token"
+	"monkey/internal/ast"
+	"monkey/internal/lexer"
+	"monkey/internal/token"
 	"strconv"
 )
 

internal/parser/parser_test.go

@@ -3,8 +3,8 @@ package parser
 import (
 	"fmt"
 	"github.com/stretchr/testify/assert"
-	"monkey/ast"
-	"monkey/lexer"
+	"monkey/internal/ast"
+	"monkey/internal/lexer"
 	"testing"
 )
 

internal/plugins/hello.go

@@ -1,6 +1,6 @@
-package main
+package internal
 
-import "monkey/object"
+import "monkey/internal/object"
 
 // Hello ...
 func Hello(args ...object.Object) object.Object {

internal/repl/repl.go

@@ -8,12 +8,12 @@ import (
 	"fmt"
 	"io"
 	"log"
-	"monkey/compiler"
-	"monkey/evaluator"
-	"monkey/lexer"
-	"monkey/object"
-	"monkey/parser"
-	"monkey/vm"
+	"monkey/internal/compiler"
+	"monkey/internal/evaluator"
+	"monkey/internal/lexer"
+	"monkey/internal/object"
+	"monkey/internal/parser"
+	"monkey/internal/vm"
 	"os"
 )
 

internal/typing/typing.go

@@ -2,7 +2,7 @@ package typing
 
 import (
 	"fmt"
-	"monkey/object"
+	"monkey/internal/object"
 )
 
 type CheckFunc func(name string, args []object.Object) error

internal/version.go

@@ -1,4 +1,4 @@
-package main
+package internal
 
 import (
 	"fmt"

internal/vm/cache.go

@@ -0,0 +1,270 @@
+package vm
+
+import (
+	"container/list"
+	"fmt"
+	"sync"
+)
+
+type cachedFrame struct {
+	Key       uint   // pointer to key
+	Value     *Frame // pointer to value
+	Frequency uint   // frequency of access
+}
+
+type frequencyNode struct {
+	count      uint          // frequency count - never decreases
+	valuesList *list.List    // valuesList contains pointer to the head of values linked list
+	inner      *list.Element // actual content of the next element
+}
+
+// creates a new frequency list node with the given count
+func newFrequencyNode(count uint) *frequencyNode {
+	return &frequencyNode{
+		count:      count,
+		valuesList: list.New(),
+		inner:      nil,
+	}
+}
+
+type keyRefNode struct {
+	inner          *list.Element // contains the actual value wrapped by a list element
+	parentFreqNode *list.Element // contains reference to the frequency node element
+	keyRef         uint          // contains pointer to the key
+	valueRef       *Frame        // value
+}
+
+// creates a new KeyRef node which is used to represent the value in linked list
+func newKeyRefNode(keyRef uint, valueRef *Frame, parent *list.Element) *keyRefNode {
+	return &keyRefNode{
+		inner:          nil,
+		parentFreqNode: parent,
+		keyRef:         keyRef,
+		valueRef:       valueRef,
+	}
+}
+
+// FrameCache implements all the methods and data-structures required for a LFU cache for caching frames.
+type FrameCache struct {
+	rwLock      sync.RWMutex         // rwLock is a read-write mutex which provides concurrent reads but exclusive writes
+	lookupTable map[uint]*keyRefNode // a hash table of <KeyType, *ValueType> for quick reference of values based on keys
+	frequencies *list.List           // internal linked list that contains frequency mapping
+	maxSize     uint                 // maxSize represents the maximum number of elements that can be in the cache before eviction
+}
+
+// MaxSize returns the maximum size of the cache at that point in time
+func (lfu *FrameCache) MaxSize() uint {
+	lfu.rwLock.RLock()
+	defer lfu.rwLock.RUnlock()
+
+	return lfu.maxSize
+}
+
+// CurrentSize returns the number of elements in that cache
+func (lfu *FrameCache) CurrentSize() uint {
+	lfu.rwLock.RLock()
+	defer lfu.rwLock.RUnlock()
+
+	return uint(len(lfu.lookupTable))
+}
+
+// IsFull checks if the LFU cache is full
+func (lfu *FrameCache) IsFull() bool {
+	lfu.rwLock.RLock()
+	defer lfu.rwLock.RUnlock()
+
+	return uint(len(lfu.lookupTable)) == lfu.maxSize
+}
+
+// SetMaxSize updates the max size of the LFU cache
+func (lfu *FrameCache) SetMaxSize(size uint) {
+	lfu.rwLock.Lock()
+	defer lfu.rwLock.Unlock()
+
+	lfu.maxSize = size
+}
+
+// evict the least recently used element from the cache, this function is unsafe to be called externally
+// because it doesn't provide locking mechanism.
+func (lfu *FrameCache) unsafeEvict() error {
+	// WARNING: This function assumes that a write lock has been held by the caller already
+
+	// get the head node of the list
+	headFreq := lfu.frequencies.Front()
+	if headFreq == nil {
+		// list is empty, this is a very unusual condition
+		return fmt.Errorf("internal error: failed to evict, empty frequency list")
+	}
+
+	headFreqInner := (headFreq.Value).(*frequencyNode)
+
+	if headFreqInner.valuesList.Len() == 0 {
+		// again this is a very unusual condition
+		return fmt.Errorf("internal error: failed to evict, empty values list")
+	}
+
+	headValuesList := headFreqInner.valuesList
+	// pop the head of this this values list
+	headValueNode := headValuesList.Front()
+	removeResult := headValuesList.Remove(headValueNode).(*keyRefNode)
+
+	// update the values list
+	headFreqInner.valuesList = headValuesList
+
+	if headFreqInner.valuesList.Len() == 0 && headFreqInner.count > 1 {
+		// this node can be removed from the frequency list
+		freqList := lfu.frequencies
+		freqList.Remove(headFreq)
+		lfu.frequencies = freqList
+	}
+
+	// remove the key from lookup table
+	key := removeResult.keyRef
+	delete(lfu.lookupTable, key)
+	return nil
+}
+
+// Put method inserts a `<KeyType, ValueType>` to the LFU cache and updates internal
+// data structures to keep track of access frequencies, if the cache is full, it evicts the
+// least frequently used value from the cache.
+func (lfu *FrameCache) Put(key uint, value *Frame) error {
+	// get write lock
+	lfu.rwLock.Lock()
+	defer lfu.rwLock.Unlock()
+
+	if _, ok := lfu.lookupTable[key]; ok {
+		// update the cache value
+		lfu.lookupTable[key].valueRef = value
+		return nil
+	}
+
+	if lfu.maxSize == uint(len(lfu.lookupTable)) {
+		lfu.unsafeEvict()
+	}
+
+	valueNode := newKeyRefNode(key, value, nil)
+
+	head := lfu.frequencies.Front()
+	if head == nil {
+		// fresh linked list
+		freqNode := newFrequencyNode(1)
+		head = lfu.frequencies.PushFront(freqNode)
+		freqNode.inner = head
+
+	} else {
+		node := head.Value.(*frequencyNode)
+		if node.count != 1 {
+			freqNode := newFrequencyNode(1)
+			head = lfu.frequencies.PushFront(freqNode)
+			freqNode.inner = head
+		}
+	}
+
+	valueNode.parentFreqNode = head
+	node := head.Value.(*frequencyNode)
+	head = node.valuesList.PushBack(valueNode)
+	valueNode.inner = head
+
+	lfu.lookupTable[key] = valueNode
+	return nil
+}
+
+// Evict can be called to manually perform eviction
+func (lfu *FrameCache) Evict() error {
+	lfu.rwLock.Lock()
+	defer lfu.rwLock.Unlock()
+
+	return lfu.unsafeEvict()
+}
+
+func (lfu *FrameCache) unsafeUpdateFrequency(valueNode *keyRefNode) {
+	parentFreqNode := valueNode.parentFreqNode
+	currentNode := parentFreqNode.Value.(*frequencyNode)
+	nextParentFreqNode := parentFreqNode.Next()
+
+	var newParent *list.Element = nil
+
+	if nextParentFreqNode == nil {
+		// this is the last node
+		// create a new node with frequency + 1
+		newFreqNode := newFrequencyNode(currentNode.count + 1)
+		lfu.frequencies.PushBack(newFreqNode)
+		newParent = parentFreqNode.Next()
+
+	} else {
+		nextNode := nextParentFreqNode.Value.(*frequencyNode)
+		if nextNode.count == (currentNode.count + 1) {
+			newParent = nextParentFreqNode
+		} else {
+			// insert a node in between
+			newFreqNode := newFrequencyNode(currentNode.count + 1)
+
+			lfu.frequencies.InsertAfter(newFreqNode, parentFreqNode)
+			newParent = parentFreqNode.Next()
+		}
+	}
+
+	// remove from the existing list
+	currentNode.valuesList.Remove(valueNode.inner)
+
+	newParentNode := newParent.Value.(*frequencyNode)
+	valueNode.parentFreqNode = newParent
+	newValueNode := newParentNode.valuesList.PushBack(valueNode)
+	valueNode.inner = newValueNode
+
+	// check if the current node is empty
+	if currentNode.valuesList.Len() == 0 {
+		// remove the current node
+		lfu.frequencies.Remove(parentFreqNode)
+	}
+}
+
+// Get can be called to obtain the value for given key
+func (lfu *FrameCache) Get(key uint) (*Frame, bool) {
+	lfu.rwLock.Lock()
+	defer lfu.rwLock.Unlock()
+
+	// check if data is in the map
+	valueNode, found := lfu.lookupTable[key]
+	if !found {
+		return nil, false
+	}
+
+	lfu.unsafeUpdateFrequency(valueNode)
+
+	return valueNode.valueRef, true
+}
+
+// Delete removes the specified entry from LFU cache
+func (lfu *FrameCache) Delete(key uint) error {
+	lfu.rwLock.Lock()
+	defer lfu.rwLock.Unlock()
+
+	// check if the key is in the map
+	valueNode, found := lfu.lookupTable[key]
+	if !found {
+		return fmt.Errorf("key %v not found", key)
+	}
+
+	parentFreqNode := valueNode.parentFreqNode
+
+	currentNode := (parentFreqNode.Value).(*frequencyNode)
+	currentNode.valuesList.Remove(valueNode.inner)
+
+	if currentNode.valuesList.Len() == 0 {
+		lfu.frequencies.Remove(parentFreqNode)
+	}
+
+	delete(lfu.lookupTable, key)
+	return nil
+}
+
+// NewFrameCache ...
+func NewFrameCache(maxSize uint) *FrameCache {
+	return &FrameCache{
+		rwLock:      sync.RWMutex{},
+		lookupTable: make(map[uint]*keyRefNode),
+		maxSize:     maxSize,
+		frequencies: list.New(),
+	}
+}

internal/vm/frame.go

@@ -1,10 +1,13 @@
 package vm
 
 import (
-	"monkey/code"
-	"monkey/object"
+	"monkey/internal/code"
+	"monkey/internal/object"
+	"unsafe"
 )
 
+var cache = NewFrameCache(32)
+
 type Frame struct {
 	cl          *object.Closure
 	ip          int
@@ -12,16 +15,32 @@ type Frame struct {
 }
 
 func NewFrame(cl *object.Closure, basePointer int) *Frame {
-	return &Frame{
+	key := uint(uintptr(unsafe.Pointer(cl))) + uint(basePointer)
+	if frame, ok := cache.Get(key); ok {
+		frame.Reset()
+		return frame
+	}
+
+	frame := &Frame{
 		cl:          cl,
 		ip:          -1,
-		basePointer: basePointer}
+		basePointer: basePointer,
+	}
+
+	cache.Put(key, frame)
+
+	return frame
+}
+
+// NextOp ...
+func (f *Frame) NextOp() code.Opcode {
+	return code.Opcode(f.Instructions()[f.ip+1])
+}
+
+func (f *Frame) Reset() {
+	f.ip = -1
 }
 
 func (f *Frame) Instructions() code.Instructions {
 	return f.cl.Fn.Instructions
 }
-
-func (f *Frame) NextOp() code.Opcode {
-	return code.Opcode(f.Instructions()[f.ip+1])
-}

internal/vm/vm.go

@@ -4,13 +4,13 @@ import (
 	"fmt"
 	"io/ioutil"
 	"log"
-	"monkey/builtins"
-	"monkey/code"
-	"monkey/compiler"
-	"monkey/lexer"
-	"monkey/object"
-	"monkey/parser"
-	"monkey/utils"
+	"monkey/internal/builtins"
+	"monkey/internal/code"
+	"monkey/internal/compiler"
+	"monkey/internal/lexer"
+	"monkey/internal/object"
+	"monkey/internal/parser"
+	"monkey/internal/utils"
 	"strings"
 	"unicode"
 )

internal/vm/vm_test.go

@@ -2,12 +2,12 @@ package vm
 
 import (
 	"fmt"
-	"monkey/ast"
-	"monkey/compiler"
-	"monkey/lexer"
-	"monkey/object"
-	"monkey/parser"
-	"monkey/utils"
+	"monkey/internal/ast"
+	"monkey/internal/compiler"
+	"monkey/internal/lexer"
+	"monkey/internal/object"
+	"monkey/internal/parser"
+	"monkey/internal/utils"
 	"os"
 	"path"
 	"path/filepath"
@@ -1185,15 +1185,15 @@ func BenchmarkFibonacci(b *testing.B) {
 func TestImportExpressions(t *testing.T) {
 	tests := []vmTestCase{
 		{
-			input:    `mod := import("../testdata/mod"); mod.A`,
+			input:    `mod := import("../../testdata/mod"); mod.A`,
 			expected: 5,
 		},
 		{
-			input:    `mod := import("../testdata/mod"); mod.Sum(2, 3)`,
+			input:    `mod := import("../../testdata/mod"); mod.Sum(2, 3)`,
 			expected: 5,
 		},
 		{
-			input:    `mod := import("../testdata/mod"); mod.a`,
+			input:    `mod := import("../../testdata/mod"); mod.a`,
 			expected: nil,
 		},
 	}
@@ -1202,11 +1202,11 @@ func TestImportExpressions(t *testing.T) {
 }
 
 func TestImportSearchPaths(t *testing.T) {
-	utils.AddPath("../testdata")
+	utils.AddPath("../../testdata")
 
 	tests := []vmTestCase{
 		{
-			input:    `mod := import("../testdata/mod"); mod.A`,
+			input:    `mod := import("../../testdata/mod"); mod.A`,
 			expected: 5,
 		},
 	}