/
iterator.go
131 lines (116 loc) · 4.42 KB
/
iterator.go
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// Copyright (c) 2015, Emir Pasic. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package doublylinkedlist
import "github.com/emirpasic/gods/containers"
// Assert Iterator implementation
var _ containers.ReverseIteratorWithIndex = (*Iterator)(nil)
// Iterator holding the iterator's state
type Iterator struct {
list *List
index int
element *element
}
// Iterator returns a stateful iterator whose values can be fetched by an index.
func (list *List) Iterator() Iterator {
return Iterator{list: list, index: -1, element: nil}
}
// Next moves the iterator to the next element and returns true if there was a next element in the container.
// If Next() returns true, then next element's index and value can be retrieved by Index() and Value().
// If Next() was called for the first time, then it will point the iterator to the first element if it exists.
// Modifies the state of the iterator.
func (iterator *Iterator) Next() bool {
if iterator.index < iterator.list.size {
iterator.index++
}
if !iterator.list.withinRange(iterator.index) {
iterator.element = nil
return false
}
if iterator.index != 0 {
iterator.element = iterator.element.next
} else {
iterator.element = iterator.list.first
}
return true
}
// Prev moves the iterator to the previous element and returns true if there was a previous element in the container.
// If Prev() returns true, then previous element's index and value can be retrieved by Index() and Value().
// Modifies the state of the iterator.
func (iterator *Iterator) Prev() bool {
if iterator.index >= 0 {
iterator.index--
}
if !iterator.list.withinRange(iterator.index) {
iterator.element = nil
return false
}
if iterator.index == iterator.list.size-1 {
iterator.element = iterator.list.last
} else {
iterator.element = iterator.element.prev
}
return iterator.list.withinRange(iterator.index)
}
// Value returns the current element's value.
// Does not modify the state of the iterator.
func (iterator *Iterator) Value() interface{} {
return iterator.element.value
}
// Index returns the current element's index.
// Does not modify the state of the iterator.
func (iterator *Iterator) Index() int {
return iterator.index
}
// Begin resets the iterator to its initial state (one-before-first)
// Call Next() to fetch the first element if any.
func (iterator *Iterator) Begin() {
iterator.index = -1
iterator.element = nil
}
// End moves the iterator past the last element (one-past-the-end).
// Call Prev() to fetch the last element if any.
func (iterator *Iterator) End() {
iterator.index = iterator.list.size
iterator.element = iterator.list.last
}
// First moves the iterator to the first element and returns true if there was a first element in the container.
// If First() returns true, then first element's index and value can be retrieved by Index() and Value().
// Modifies the state of the iterator.
func (iterator *Iterator) First() bool {
iterator.Begin()
return iterator.Next()
}
// Last moves the iterator to the last element and returns true if there was a last element in the container.
// If Last() returns true, then last element's index and value can be retrieved by Index() and Value().
// Modifies the state of the iterator.
func (iterator *Iterator) Last() bool {
iterator.End()
return iterator.Prev()
}
// NextTo moves the iterator to the next element from current position that satisfies the condition given by the
// passed function, and returns true if there was a next element in the container.
// If NextTo() returns true, then next element's index and value can be retrieved by Index() and Value().
// Modifies the state of the iterator.
func (iterator *Iterator) NextTo(f func(index int, value interface{}) bool) bool {
for iterator.Next() {
index, value := iterator.Index(), iterator.Value()
if f(index, value) {
return true
}
}
return false
}
// PrevTo moves the iterator to the previous element from current position that satisfies the condition given by the
// passed function, and returns true if there was a next element in the container.
// If PrevTo() returns true, then next element's index and value can be retrieved by Index() and Value().
// Modifies the state of the iterator.
func (iterator *Iterator) PrevTo(f func(index int, value interface{}) bool) bool {
for iterator.Prev() {
index, value := iterator.Index(), iterator.Value()
if f(index, value) {
return true
}
}
return false
}