github.com/alexandrestein/gods@v1.0.1/lists/arraylist/iterator.go (about)

     1  // Copyright (c) 2015, Emir Pasic. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package arraylist
     6  
     7  import "github.com/alexandrestein/gods/containers"
     8  
     9  func assertIteratorImplementation() {
    10  	var _ containers.ReverseIteratorWithIndex = (*Iterator)(nil)
    11  }
    12  
    13  // Iterator holding the iterator's state
    14  type Iterator struct {
    15  	list  *List
    16  	index int
    17  }
    18  
    19  // Iterator returns a stateful iterator whose values can be fetched by an index.
    20  func (list *List) Iterator() Iterator {
    21  	return Iterator{list: list, index: -1}
    22  }
    23  
    24  // Next moves the iterator to the next element and returns true if there was a next element in the container.
    25  // If Next() returns true, then next element's index and value can be retrieved by Index() and Value().
    26  // If Next() was called for the first time, then it will point the iterator to the first element if it exists.
    27  // Modifies the state of the iterator.
    28  func (iterator *Iterator) Next() bool {
    29  	if iterator.index < iterator.list.size {
    30  		iterator.index++
    31  	}
    32  	return iterator.list.withinRange(iterator.index)
    33  }
    34  
    35  // Prev moves the iterator to the previous element and returns true if there was a previous element in the container.
    36  // If Prev() returns true, then previous element's index and value can be retrieved by Index() and Value().
    37  // Modifies the state of the iterator.
    38  func (iterator *Iterator) Prev() bool {
    39  	if iterator.index >= 0 {
    40  		iterator.index--
    41  	}
    42  	return iterator.list.withinRange(iterator.index)
    43  }
    44  
    45  // Value returns the current element's value.
    46  // Does not modify the state of the iterator.
    47  func (iterator *Iterator) Value() interface{} {
    48  	return iterator.list.elements[iterator.index]
    49  }
    50  
    51  // Index returns the current element's index.
    52  // Does not modify the state of the iterator.
    53  func (iterator *Iterator) Index() int {
    54  	return iterator.index
    55  }
    56  
    57  // Begin resets the iterator to its initial state (one-before-first)
    58  // Call Next() to fetch the first element if any.
    59  func (iterator *Iterator) Begin() {
    60  	iterator.index = -1
    61  }
    62  
    63  // End moves the iterator past the last element (one-past-the-end).
    64  // Call Prev() to fetch the last element if any.
    65  func (iterator *Iterator) End() {
    66  	iterator.index = iterator.list.size
    67  }
    68  
    69  // First moves the iterator to the first element and returns true if there was a first element in the container.
    70  // If First() returns true, then first element's index and value can be retrieved by Index() and Value().
    71  // Modifies the state of the iterator.
    72  func (iterator *Iterator) First() bool {
    73  	iterator.Begin()
    74  	return iterator.Next()
    75  }
    76  
    77  // Last moves the iterator to the last element and returns true if there was a last element in the container.
    78  // If Last() returns true, then last element's index and value can be retrieved by Index() and Value().
    79  // Modifies the state of the iterator.
    80  func (iterator *Iterator) Last() bool {
    81  	iterator.End()
    82  	return iterator.Prev()
    83  }