mirror of
https://github.com/golang/go
synced 2024-09-04 15:34:21 +00:00
![Matthew Dempsky](/assets/img/avatar_default.png)
The next CL will remove the -G flag, effectively hard-coding it to its current default (-G=3). Change-Id: Ib4743b529206928f9f1cca9fdb19989728327831 Reviewed-on: https://go-review.googlesource.com/c/go/+/388534 Reviewed-by: Keith Randall <khr@golang.org> Trust: Matthew Dempsky <mdempsky@google.com> Run-TryBot: Matthew Dempsky <mdempsky@google.com> TryBot-Result: Gopher Robot <gobot@golang.org>
609 lines
15 KiB
Go
609 lines
15 KiB
Go
// run
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// Copyright 2021 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package list provides a doubly linked list of some element type
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// (generic form of the "container/list" package).
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package main
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import (
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"fmt"
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"strconv"
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)
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// Element is an element of a linked list.
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type _Element[T any] struct {
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// Next and previous pointers in the doubly-linked list of elements.
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// To simplify the implementation, internally a list l is implemented
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// as a ring, such that &l.root is both the next element of the last
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// list element (l.Back()) and the previous element of the first list
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// element (l.Front()).
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next, prev *_Element[T]
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// The list to which this element belongs.
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list *_List[T]
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// The value stored with this element.
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Value T
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}
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// Next returns the next list element or nil.
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func (e *_Element[T]) Next() *_Element[T] {
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if p := e.next; e.list != nil && p != &e.list.root {
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return p
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}
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return nil
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}
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// Prev returns the previous list element or nil.
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func (e *_Element[T]) Prev() *_Element[T] {
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if p := e.prev; e.list != nil && p != &e.list.root {
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return p
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}
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return nil
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}
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// _List represents a doubly linked list.
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// The zero value for _List is an empty list ready to use.
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type _List[T any] struct {
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root _Element[T] // sentinel list element, only &root, root.prev, and root.next are used
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len int // current list length excluding (this) sentinel element
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}
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// Init initializes or clears list l.
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func (l *_List[T]) Init() *_List[T] {
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l.root.next = &l.root
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l.root.prev = &l.root
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l.len = 0
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return l
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}
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// New returns an initialized list.
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func _New[T any]() *_List[T] { return new(_List[T]).Init() }
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// Len returns the number of elements of list l.
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// The complexity is O(1).
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func (l *_List[_]) Len() int { return l.len }
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// Front returns the first element of list l or nil if the list is empty.
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func (l *_List[T]) Front() *_Element[T] {
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if l.len == 0 {
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return nil
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}
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return l.root.next
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}
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// Back returns the last element of list l or nil if the list is empty.
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func (l *_List[T]) Back() *_Element[T] {
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if l.len == 0 {
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return nil
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}
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return l.root.prev
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}
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// lazyInit lazily initializes a zero _List value.
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func (l *_List[_]) lazyInit() {
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if l.root.next == nil {
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l.Init()
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}
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}
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// insert inserts e after at, increments l.len, and returns e.
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func (l *_List[T]) insert(e, at *_Element[T]) *_Element[T] {
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e.prev = at
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e.next = at.next
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e.prev.next = e
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e.next.prev = e
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e.list = l
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l.len++
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return e
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}
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// insertValue is a convenience wrapper for insert(&_Element[T]{Value: v}, at).
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func (l *_List[T]) insertValue(v T, at *_Element[T]) *_Element[T] {
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return l.insert(&_Element[T]{Value: v}, at)
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}
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// remove removes e from its list, decrements l.len, and returns e.
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func (l *_List[T]) remove(e *_Element[T]) *_Element[T] {
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e.prev.next = e.next
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e.next.prev = e.prev
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e.next = nil // avoid memory leaks
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e.prev = nil // avoid memory leaks
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e.list = nil
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l.len--
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return e
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}
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// move moves e to next to at and returns e.
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func (l *_List[T]) move(e, at *_Element[T]) *_Element[T] {
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if e == at {
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return e
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}
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e.prev.next = e.next
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e.next.prev = e.prev
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e.prev = at
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e.next = at.next
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e.prev.next = e
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e.next.prev = e
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return e
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}
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// Remove removes e from l if e is an element of list l.
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// It returns the element value e.Value.
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// The element must not be nil.
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func (l *_List[T]) Remove(e *_Element[T]) T {
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if e.list == l {
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// if e.list == l, l must have been initialized when e was inserted
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// in l or l == nil (e is a zero _Element) and l.remove will crash
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l.remove(e)
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}
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return e.Value
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}
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// PushFront inserts a new element e with value v at the front of list l and returns e.
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func (l *_List[T]) PushFront(v T) *_Element[T] {
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l.lazyInit()
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return l.insertValue(v, &l.root)
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}
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// PushBack inserts a new element e with value v at the back of list l and returns e.
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func (l *_List[T]) PushBack(v T) *_Element[T] {
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l.lazyInit()
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return l.insertValue(v, l.root.prev)
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}
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// InsertBefore inserts a new element e with value v immediately before mark and returns e.
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// If mark is not an element of l, the list is not modified.
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// The mark must not be nil.
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func (l *_List[T]) InsertBefore(v T, mark *_Element[T]) *_Element[T] {
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if mark.list != l {
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return nil
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}
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// see comment in _List.Remove about initialization of l
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return l.insertValue(v, mark.prev)
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}
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// InsertAfter inserts a new element e with value v immediately after mark and returns e.
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// If mark is not an element of l, the list is not modified.
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// The mark must not be nil.
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func (l *_List[T]) InsertAfter(v T, mark *_Element[T]) *_Element[T] {
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if mark.list != l {
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return nil
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}
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// see comment in _List.Remove about initialization of l
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return l.insertValue(v, mark)
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}
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// MoveToFront moves element e to the front of list l.
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// If e is not an element of l, the list is not modified.
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// The element must not be nil.
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func (l *_List[T]) MoveToFront(e *_Element[T]) {
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if e.list != l || l.root.next == e {
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return
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}
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// see comment in _List.Remove about initialization of l
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l.move(e, &l.root)
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}
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// MoveToBack moves element e to the back of list l.
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// If e is not an element of l, the list is not modified.
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// The element must not be nil.
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func (l *_List[T]) MoveToBack(e *_Element[T]) {
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if e.list != l || l.root.prev == e {
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return
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}
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// see comment in _List.Remove about initialization of l
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l.move(e, l.root.prev)
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}
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// MoveBefore moves element e to its new position before mark.
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// If e or mark is not an element of l, or e == mark, the list is not modified.
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// The element and mark must not be nil.
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func (l *_List[T]) MoveBefore(e, mark *_Element[T]) {
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if e.list != l || e == mark || mark.list != l {
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return
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}
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l.move(e, mark.prev)
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}
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// MoveAfter moves element e to its new position after mark.
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// If e or mark is not an element of l, or e == mark, the list is not modified.
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// The element and mark must not be nil.
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func (l *_List[T]) MoveAfter(e, mark *_Element[T]) {
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if e.list != l || e == mark || mark.list != l {
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return
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}
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l.move(e, mark)
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}
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// PushBackList inserts a copy of an other list at the back of list l.
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// The lists l and other may be the same. They must not be nil.
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func (l *_List[T]) PushBackList(other *_List[T]) {
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l.lazyInit()
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for i, e := other.Len(), other.Front(); i > 0; i, e = i-1, e.Next() {
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l.insertValue(e.Value, l.root.prev)
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}
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}
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// PushFrontList inserts a copy of an other list at the front of list l.
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// The lists l and other may be the same. They must not be nil.
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func (l *_List[T]) PushFrontList(other *_List[T]) {
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l.lazyInit()
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for i, e := other.Len(), other.Back(); i > 0; i, e = i-1, e.Prev() {
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l.insertValue(e.Value, &l.root)
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}
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}
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// Transform runs a transform function on a list returning a new list.
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func _Transform[TElem1, TElem2 any](lst *_List[TElem1], f func(TElem1) TElem2) *_List[TElem2] {
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ret := _New[TElem2]()
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for p := lst.Front(); p != nil; p = p.Next() {
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ret.PushBack(f(p.Value))
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}
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return ret
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}
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func checkListLen[T any](l *_List[T], len int) bool {
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if n := l.Len(); n != len {
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panic(fmt.Sprintf("l.Len() = %d, want %d", n, len))
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return false
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}
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return true
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}
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func checkListPointers[T any](l *_List[T], es []*_Element[T]) {
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root := &l.root
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if !checkListLen(l, len(es)) {
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return
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}
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// zero length lists must be the zero value or properly initialized (sentinel circle)
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if len(es) == 0 {
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if l.root.next != nil && l.root.next != root || l.root.prev != nil && l.root.prev != root {
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panic(fmt.Sprintf("l.root.next = %p, l.root.prev = %p; both should both be nil or %p", l.root.next, l.root.prev, root))
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}
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return
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}
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// len(es) > 0
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// check internal and external prev/next connections
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for i, e := range es {
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prev := root
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Prev := (*_Element[T])(nil)
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if i > 0 {
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prev = es[i-1]
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Prev = prev
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}
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if p := e.prev; p != prev {
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panic(fmt.Sprintf("elt[%d](%p).prev = %p, want %p", i, e, p, prev))
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}
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if p := e.Prev(); p != Prev {
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panic(fmt.Sprintf("elt[%d](%p).Prev() = %p, want %p", i, e, p, Prev))
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}
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next := root
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Next := (*_Element[T])(nil)
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if i < len(es)-1 {
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next = es[i+1]
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Next = next
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}
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if n := e.next; n != next {
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panic(fmt.Sprintf("elt[%d](%p).next = %p, want %p", i, e, n, next))
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}
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if n := e.Next(); n != Next {
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panic(fmt.Sprintf("elt[%d](%p).Next() = %p, want %p", i, e, n, Next))
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}
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}
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}
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func TestList() {
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l := _New[string]()
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checkListPointers(l, []*(_Element[string]){})
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// Single element list
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e := l.PushFront("a")
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checkListPointers(l, []*(_Element[string]){e})
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l.MoveToFront(e)
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checkListPointers(l, []*(_Element[string]){e})
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l.MoveToBack(e)
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checkListPointers(l, []*(_Element[string]){e})
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l.Remove(e)
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checkListPointers(l, []*(_Element[string]){})
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// Bigger list
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l2 := _New[int]()
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e2 := l2.PushFront(2)
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e1 := l2.PushFront(1)
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e3 := l2.PushBack(3)
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e4 := l2.PushBack(600)
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checkListPointers(l2, []*(_Element[int]){e1, e2, e3, e4})
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l2.Remove(e2)
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checkListPointers(l2, []*(_Element[int]){e1, e3, e4})
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l2.MoveToFront(e3) // move from middle
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checkListPointers(l2, []*(_Element[int]){e3, e1, e4})
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l2.MoveToFront(e1)
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l2.MoveToBack(e3) // move from middle
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checkListPointers(l2, []*(_Element[int]){e1, e4, e3})
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l2.MoveToFront(e3) // move from back
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checkListPointers(l2, []*(_Element[int]){e3, e1, e4})
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l2.MoveToFront(e3) // should be no-op
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checkListPointers(l2, []*(_Element[int]){e3, e1, e4})
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l2.MoveToBack(e3) // move from front
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checkListPointers(l2, []*(_Element[int]){e1, e4, e3})
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l2.MoveToBack(e3) // should be no-op
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checkListPointers(l2, []*(_Element[int]){e1, e4, e3})
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e2 = l2.InsertBefore(2, e1) // insert before front
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checkListPointers(l2, []*(_Element[int]){e2, e1, e4, e3})
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l2.Remove(e2)
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e2 = l2.InsertBefore(2, e4) // insert before middle
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checkListPointers(l2, []*(_Element[int]){e1, e2, e4, e3})
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l2.Remove(e2)
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e2 = l2.InsertBefore(2, e3) // insert before back
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checkListPointers(l2, []*(_Element[int]){e1, e4, e2, e3})
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l2.Remove(e2)
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e2 = l2.InsertAfter(2, e1) // insert after front
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checkListPointers(l2, []*(_Element[int]){e1, e2, e4, e3})
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l2.Remove(e2)
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e2 = l2.InsertAfter(2, e4) // insert after middle
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checkListPointers(l2, []*(_Element[int]){e1, e4, e2, e3})
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l2.Remove(e2)
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e2 = l2.InsertAfter(2, e3) // insert after back
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checkListPointers(l2, []*(_Element[int]){e1, e4, e3, e2})
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l2.Remove(e2)
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// Check standard iteration.
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sum := 0
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for e := l2.Front(); e != nil; e = e.Next() {
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sum += e.Value
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}
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if sum != 604 {
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panic(fmt.Sprintf("sum over l = %d, want 604", sum))
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}
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// Clear all elements by iterating
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var next *_Element[int]
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for e := l2.Front(); e != nil; e = next {
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next = e.Next()
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l2.Remove(e)
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}
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checkListPointers(l2, []*(_Element[int]){})
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}
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func checkList[T comparable](l *_List[T], es []interface{}) {
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if !checkListLen(l, len(es)) {
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return
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}
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i := 0
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for e := l.Front(); e != nil; e = e.Next() {
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le := e.Value
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// Comparison between a generically-typed variable le and an interface.
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if le != es[i] {
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panic(fmt.Sprintf("elt[%d].Value = %v, want %v", i, le, es[i]))
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}
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i++
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}
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}
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func TestExtending() {
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l1 := _New[int]()
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l2 := _New[int]()
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l1.PushBack(1)
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l1.PushBack(2)
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l1.PushBack(3)
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l2.PushBack(4)
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l2.PushBack(5)
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l3 := _New[int]()
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l3.PushBackList(l1)
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checkList(l3, []interface{}{1, 2, 3})
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l3.PushBackList(l2)
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checkList(l3, []interface{}{1, 2, 3, 4, 5})
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l3 = _New[int]()
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l3.PushFrontList(l2)
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checkList(l3, []interface{}{4, 5})
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l3.PushFrontList(l1)
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checkList(l3, []interface{}{1, 2, 3, 4, 5})
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checkList(l1, []interface{}{1, 2, 3})
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checkList(l2, []interface{}{4, 5})
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l3 = _New[int]()
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l3.PushBackList(l1)
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checkList(l3, []interface{}{1, 2, 3})
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l3.PushBackList(l3)
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checkList(l3, []interface{}{1, 2, 3, 1, 2, 3})
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l3 = _New[int]()
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l3.PushFrontList(l1)
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checkList(l3, []interface{}{1, 2, 3})
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l3.PushFrontList(l3)
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checkList(l3, []interface{}{1, 2, 3, 1, 2, 3})
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l3 = _New[int]()
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l1.PushBackList(l3)
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checkList(l1, []interface{}{1, 2, 3})
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l1.PushFrontList(l3)
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checkList(l1, []interface{}{1, 2, 3})
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}
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func TestRemove() {
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l := _New[int]()
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e1 := l.PushBack(1)
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e2 := l.PushBack(2)
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checkListPointers(l, []*(_Element[int]){e1, e2})
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e := l.Front()
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l.Remove(e)
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checkListPointers(l, []*(_Element[int]){e2})
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l.Remove(e)
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checkListPointers(l, []*(_Element[int]){e2})
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}
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func TestIssue4103() {
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l1 := _New[int]()
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l1.PushBack(1)
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l1.PushBack(2)
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l2 := _New[int]()
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l2.PushBack(3)
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l2.PushBack(4)
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e := l1.Front()
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l2.Remove(e) // l2 should not change because e is not an element of l2
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if n := l2.Len(); n != 2 {
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panic(fmt.Sprintf("l2.Len() = %d, want 2", n))
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}
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l1.InsertBefore(8, e)
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if n := l1.Len(); n != 3 {
|
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panic(fmt.Sprintf("l1.Len() = %d, want 3", n))
|
|
}
|
|
}
|
|
|
|
func TestIssue6349() {
|
|
l := _New[int]()
|
|
l.PushBack(1)
|
|
l.PushBack(2)
|
|
|
|
e := l.Front()
|
|
l.Remove(e)
|
|
if e.Value != 1 {
|
|
panic(fmt.Sprintf("e.value = %d, want 1", e.Value))
|
|
}
|
|
if e.Next() != nil {
|
|
panic(fmt.Sprintf("e.Next() != nil"))
|
|
}
|
|
if e.Prev() != nil {
|
|
panic(fmt.Sprintf("e.Prev() != nil"))
|
|
}
|
|
}
|
|
|
|
func TestMove() {
|
|
l := _New[int]()
|
|
e1 := l.PushBack(1)
|
|
e2 := l.PushBack(2)
|
|
e3 := l.PushBack(3)
|
|
e4 := l.PushBack(4)
|
|
|
|
l.MoveAfter(e3, e3)
|
|
checkListPointers(l, []*(_Element[int]){e1, e2, e3, e4})
|
|
l.MoveBefore(e2, e2)
|
|
checkListPointers(l, []*(_Element[int]){e1, e2, e3, e4})
|
|
|
|
l.MoveAfter(e3, e2)
|
|
checkListPointers(l, []*(_Element[int]){e1, e2, e3, e4})
|
|
l.MoveBefore(e2, e3)
|
|
checkListPointers(l, []*(_Element[int]){e1, e2, e3, e4})
|
|
|
|
l.MoveBefore(e2, e4)
|
|
checkListPointers(l, []*(_Element[int]){e1, e3, e2, e4})
|
|
e2, e3 = e3, e2
|
|
|
|
l.MoveBefore(e4, e1)
|
|
checkListPointers(l, []*(_Element[int]){e4, e1, e2, e3})
|
|
e1, e2, e3, e4 = e4, e1, e2, e3
|
|
|
|
l.MoveAfter(e4, e1)
|
|
checkListPointers(l, []*(_Element[int]){e1, e4, e2, e3})
|
|
e2, e3, e4 = e4, e2, e3
|
|
|
|
l.MoveAfter(e2, e3)
|
|
checkListPointers(l, []*(_Element[int]){e1, e3, e2, e4})
|
|
e2, e3 = e3, e2
|
|
}
|
|
|
|
// Test PushFront, PushBack, PushFrontList, PushBackList with uninitialized _List
|
|
func TestZeroList() {
|
|
var l1 = new(_List[int])
|
|
l1.PushFront(1)
|
|
checkList(l1, []interface{}{1})
|
|
|
|
var l2 = new(_List[int])
|
|
l2.PushBack(1)
|
|
checkList(l2, []interface{}{1})
|
|
|
|
var l3 = new(_List[int])
|
|
l3.PushFrontList(l1)
|
|
checkList(l3, []interface{}{1})
|
|
|
|
var l4 = new(_List[int])
|
|
l4.PushBackList(l2)
|
|
checkList(l4, []interface{}{1})
|
|
}
|
|
|
|
// Test that a list l is not modified when calling InsertBefore with a mark that is not an element of l.
|
|
func TestInsertBeforeUnknownMark() {
|
|
var l _List[int]
|
|
l.PushBack(1)
|
|
l.PushBack(2)
|
|
l.PushBack(3)
|
|
l.InsertBefore(1, new(_Element[int]))
|
|
checkList(&l, []interface{}{1, 2, 3})
|
|
}
|
|
|
|
// Test that a list l is not modified when calling InsertAfter with a mark that is not an element of l.
|
|
func TestInsertAfterUnknownMark() {
|
|
var l _List[int]
|
|
l.PushBack(1)
|
|
l.PushBack(2)
|
|
l.PushBack(3)
|
|
l.InsertAfter(1, new(_Element[int]))
|
|
checkList(&l, []interface{}{1, 2, 3})
|
|
}
|
|
|
|
// Test that a list l is not modified when calling MoveAfter or MoveBefore with a mark that is not an element of l.
|
|
func TestMoveUnknownMark() {
|
|
var l1 _List[int]
|
|
e1 := l1.PushBack(1)
|
|
|
|
var l2 _List[int]
|
|
e2 := l2.PushBack(2)
|
|
|
|
l1.MoveAfter(e1, e2)
|
|
checkList(&l1, []interface{}{1})
|
|
checkList(&l2, []interface{}{2})
|
|
|
|
l1.MoveBefore(e1, e2)
|
|
checkList(&l1, []interface{}{1})
|
|
checkList(&l2, []interface{}{2})
|
|
}
|
|
|
|
// Test the Transform function.
|
|
func TestTransform() {
|
|
l1 := _New[int]()
|
|
l1.PushBack(1)
|
|
l1.PushBack(2)
|
|
l2 := _Transform(l1, strconv.Itoa)
|
|
checkList(l2, []interface{}{"1", "2"})
|
|
}
|
|
|
|
func main() {
|
|
TestList()
|
|
TestExtending()
|
|
TestRemove()
|
|
TestIssue4103()
|
|
TestIssue6349()
|
|
TestMove()
|
|
TestZeroList()
|
|
TestInsertBeforeUnknownMark()
|
|
TestInsertAfterUnknownMark()
|
|
TestTransform()
|
|
}
|