started work on porting it to golang

go/stack.go

@@ -0,0 +1,132 @@
+package main
+
+import (
+	"container/list"
+	"fmt"
+	"sync"
+)
+
+type Stack struct {
+	dll       list.List
+	backup    list.List
+	debug     bool
+	rev       int
+	backuprev int
+	mutex     sync.Mutex
+}
+
+func NewStack() *Stack {
+	return &Stack{dll: list.List{}, backup: list.List{}, rev: 0, backuprev: 0}
+}
+
+func (s *Stack) Debug(msg string) {
+	if s.debug {
+		fmt.Printf("DEBUG(%03d): %s\n", s.rev, msg)
+	}
+}
+
+func (s *Stack) ToggleDebug() {
+	s.debug = !s.debug
+}
+
+func (s *Stack) Bump() {
+	s.rev++
+}
+
+func (s *Stack) Push(x float64) {
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+
+	s.Debug(fmt.Sprintf("     push to stack: %.2f", x))
+
+	s.Bump()
+	s.dll.PushBack(x)
+}
+
+func (s *Stack) Pop() float64 {
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+
+	if s.dll.Len() == 0 {
+		return 0
+	}
+
+	tail := s.dll.Back()
+	val := tail.Value
+	s.dll.Remove(tail)
+
+	s.Debug(fmt.Sprintf("DEBUG: remove from stack: %.2f", val))
+
+	s.Bump()
+	return val.(float64)
+}
+
+func (s *Stack) Shift() {
+	s.mutex.Lock()
+	defer s.mutex.Unlock()
+
+	if s.dll.Len() == 0 {
+		return
+	}
+
+	tail := s.dll.Back()
+	s.dll.Remove(tail)
+
+	s.Debug(fmt.Sprintf("DEBUG: remove from stack: %.2f", tail.Value))
+}
+
+func (s *Stack) Last() float64 {
+	if s.dll.Back() == nil {
+		return 0
+	}
+
+	return s.dll.Back().Value.(float64)
+}
+
+func (s *Stack) Dump() {
+	fmt.Printf("Stack revision %d (%p):\n", s.rev, &s.dll)
+	for e := s.dll.Front(); e != nil; e = e.Next() {
+		fmt.Println(e.Value)
+	}
+
+	if s.debug {
+		fmt.Printf("Backup stack revision %d (%p):\n", s.backuprev, &s.backup)
+		for e := s.backup.Front(); e != nil; e = e.Next() {
+			fmt.Println(e.Value)
+		}
+	}
+}
+
+func (s *Stack) Clear() {
+	s.Debug("DEBUG: clearing stack")
+
+	s.dll = list.List{}
+}
+
+func (s *Stack) Len() int {
+	return s.dll.Len()
+}
+
+func (s *Stack) Backup() {
+	// we need clean the list and restore it from scratch each time we
+	// make a backup, because the elements in list.List{} are pointers
+	// and lead to unexpected  results. The methid here works reliably
+	// at least.
+	s.backup = list.List{}
+	for e := s.dll.Front(); e != nil; e = e.Next() {
+		s.backup.PushBack(e.Value)
+	}
+	s.backuprev = s.rev
+}
+
+func (s *Stack) Restore() {
+	if s.rev == 0 {
+		fmt.Println("error: stack is empty.")
+		return
+	}
+
+	s.Debug(fmt.Sprintf("restoring stack to revision %d", s.backuprev))
+
+	s.rev = s.backuprev
+	s.dll = s.backup
+}