peridot/vendor/github.com/emirpasic/gods/containers/iterator.go

// 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 containers

// IteratorWithIndex is stateful iterator for ordered containers whose values can be fetched by an index.
type IteratorWithIndex interface {
	// 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.
	Next() bool

	// Value returns the current element's value.
	// Does not modify the state of the iterator.
	Value() interface{}

	// Index returns the current element's index.
	// Does not modify the state of the iterator.
	Index() int

	// Begin resets the iterator to its initial state (one-before-first)
	// Call Next() to fetch the first element if any.
	Begin()

	// 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.
	First() bool
}

// IteratorWithKey is a stateful iterator for ordered containers whose elements are key value pairs.
type IteratorWithKey interface {
	// 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 key and value can be retrieved by Key() 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.
	Next() bool

	// Value returns the current element's value.
	// Does not modify the state of the iterator.
	Value() interface{}

	// Key returns the current element's key.
	// Does not modify the state of the iterator.
	Key() interface{}

	// Begin resets the iterator to its initial state (one-before-first)
	// Call Next() to fetch the first element if any.
	Begin()

	// 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 key and value can be retrieved by Key() and Value().
	// Modifies the state of the iterator.
	First() bool
}

// ReverseIteratorWithIndex is stateful iterator for ordered containers whose values can be fetched by an index.
//
// Essentially it is the same as IteratorWithIndex, but provides additional:
//
// Prev() function to enable traversal in reverse
//
// Last() function to move the iterator to the last element.
//
// End() function to move the iterator past the last element (one-past-the-end).
type ReverseIteratorWithIndex interface {
	// 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.
	Prev() bool

	// End moves the iterator past the last element (one-past-the-end).
	// Call Prev() to fetch the last element if any.
	End()

	// 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.
	Last() bool

	IteratorWithIndex
}

// ReverseIteratorWithKey is a stateful iterator for ordered containers whose elements are key value pairs.
//
// Essentially it is the same as IteratorWithKey, but provides additional:
//
// Prev() function to enable traversal in reverse
//
// Last() function to move the iterator to the last element.
type ReverseIteratorWithKey interface {
	// 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 key and value can be retrieved by Key() and Value().
	// Modifies the state of the iterator.
	Prev() bool

	// End moves the iterator past the last element (one-past-the-end).
	// Call Prev() to fetch the last element if any.
	End()

	// 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 key and value can be retrieved by Key() and Value().
	// Modifies the state of the iterator.
	Last() bool

	IteratorWithKey
}