Source: list.go in package container/list

Package list implements a doubly linked list. To iterate over a list (where l is a *List): for e := l.Front(); e != nil; e = e.Next() { // do something with e.Value }

package list

Element is an element of a linked list.

Next and previous pointers in the doubly-linked list of elements. To simplify the implementation, internally a list l is implemented as a ring, such that &l.root is both the next element of the last list element (l.Back()) and the previous element of the first list element (l.Front()).

	next, prev *Element

The list to which this element belongs.

	list *List

The value stored with this element.

	Value interface{}
}

Next returns the next list element or nil.

func (e *Element) Next() *Element {
	if p := e.next; e.list != nil && p != &e.list.root {
		return p
	}
	return nil
}

Prev returns the previous list element or nil.

func (e *Element) Prev() *Element {
	if p := e.prev; e.list != nil && p != &e.list.root {
		return p
	}
	return nil
}

List represents a doubly linked list. The zero value for List is an empty list ready to use.

type List struct {
	root Element // sentinel list element, only &root, root.prev, and root.next are used
	len  int     // current list length excluding (this) sentinel element
}

Init initializes or clears list l.

func (l *List) Init() *List {
	l.root.next = &l.root
	l.root.prev = &l.root
	l.len = 0
	return l
}

New returns an initialized list.

func New() *List { return new(List).Init() }

Len returns the number of elements of list l. The complexity is O(1).

func (l *List) Len() int { return l.len }

Front returns the first element of list l or nil if the list is empty.

func (l *List) Front() *Element {
	if l.len == 0 {
		return nil
	}
	return l.root.next
}

Back returns the last element of list l or nil if the list is empty.

func (l *List) Back() *Element {
	if l.len == 0 {
		return nil
	}
	return l.root.prev
}

lazyInit lazily initializes a zero List value.

func (l *List) lazyInit() {
	if l.root.next == nil {
		l.Init()
	}
}

insert inserts e after at, increments l.len, and returns e.

func (l *List) insert(e, at *Element) *Element {
	e.prev = at
	e.next = at.next
	e.prev.next = e
	e.next.prev = e
	e.list = l
	l.len++
	return e
}

insertValue is a convenience wrapper for insert(&Element{Value: v}, at).

func (l *List) insertValue(v interface{}, at *Element) *Element {
	return l.insert(&Element{Value: v}, at)
}

remove removes e from its list, decrements l.len, and returns e.

func (l *List) remove(e *Element) *Element {
	e.prev.next = e.next
	e.next.prev = e.prev
	e.next = nil // avoid memory leaks
	e.prev = nil // avoid memory leaks
	e.list = nil
	l.len--
	return e
}

move moves e to next to at and returns e.

func (l *List) move(e, at *Element) *Element {
	if e == at {
		return e
	}
	e.prev.next = e.next
	e.next.prev = e.prev

	e.prev = at
	e.next = at.next
	e.prev.next = e
	e.next.prev = e

	return e
}

Remove removes e from l if e is an element of list l. It returns the element value e.Value. The element must not be nil.

func (l *List) Remove(e *Element) interface{} {

if e.list == l, l must have been initialized when e was inserted in l or l == nil (e is a zero Element) and l.remove will crash

		l.remove(e)
	}
	return e.Value
}

PushFront inserts a new element e with value v at the front of list l and returns e.

func (l *List) PushFront(v interface{}) *Element {
	l.lazyInit()
	return l.insertValue(v, &l.root)
}

PushBack inserts a new element e with value v at the back of list l and returns e.

func (l *List) PushBack(v interface{}) *Element {
	l.lazyInit()
	return l.insertValue(v, l.root.prev)
}

InsertBefore inserts a new element e with value v immediately before mark and returns e. If mark is not an element of l, the list is not modified. The mark must not be nil.

func (l *List) InsertBefore(v interface{}, mark *Element) *Element {
	if mark.list != l {
		return nil

see comment in List.Remove about initialization of l

	return l.insertValue(v, mark.prev)
}

InsertAfter inserts a new element e with value v immediately after mark and returns e. If mark is not an element of l, the list is not modified. The mark must not be nil.

func (l *List) InsertAfter(v interface{}, mark *Element) *Element {
	if mark.list != l {
		return nil

see comment in List.Remove about initialization of l

	return l.insertValue(v, mark)
}

MoveToFront moves element e to the front of list l. If e is not an element of l, the list is not modified. The element must not be nil.

func (l *List) MoveToFront(e *Element) {
	if e.list != l || l.root.next == e {
		return

see comment in List.Remove about initialization of l

	l.move(e, &l.root)
}

MoveToBack moves element e to the back of list l. If e is not an element of l, the list is not modified. The element must not be nil.

func (l *List) MoveToBack(e *Element) {
	if e.list != l || l.root.prev == e {
		return

see comment in List.Remove about initialization of l

	l.move(e, l.root.prev)
}

MoveBefore moves element e to its new position before mark. If e or mark is not an element of l, or e == mark, the list is not modified. The element and mark must not be nil.

func (l *List) MoveBefore(e, mark *Element) {
	if e.list != l || e == mark || mark.list != l {
		return
	}
	l.move(e, mark.prev)
}

MoveAfter moves element e to its new position after mark. If e or mark is not an element of l, or e == mark, the list is not modified. The element and mark must not be nil.

func (l *List) MoveAfter(e, mark *Element) {
	if e.list != l || e == mark || mark.list != l {
		return
	}
	l.move(e, mark)
}

PushBackList inserts a copy of another list at the back of list l. The lists l and other may be the same. They must not be nil.

func (l *List) PushBackList(other *List) {
	l.lazyInit()
	for i, e := other.Len(), other.Front(); i > 0; i, e = i-1, e.Next() {
		l.insertValue(e.Value, l.root.prev)
	}
}

PushFrontList inserts a copy of another list at the front of list l. The lists l and other may be the same. They must not be nil.

func (l *List) PushFrontList(other *List) {
	l.lazyInit()
	for i, e := other.Len(), other.Back(); i > 0; i, e = i-1, e.Prev() {
		l.insertValue(e.Value, &l.root)
	}