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.
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.
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).
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.
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