gods/containers/iterator.go

/*
Copyright (c) 2015, Emir Pasic
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

* Redistributions of source code must retain the above copyright notice, this
  list of conditions and the following disclaimer.

* Redistributions in binary form must reproduce the above copyright notice,
  this list of conditions and the following disclaimer in the documentation
  and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

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
}