Hi!

What's the relation between std::iterator and the iterators provided
by various containers? How do the concepts of five categories of
iterators be implementated by these iterator classes including
std::iterator and various container iterators?

Thank you for your time.

lovecreatesbea...@gmail.com a écrit :
> Hi!
>
> What's the relation between std::iterator and the iterators provided
> by various containers? How do the concepts of five categories of
> iterators be implementated by these iterator classes including
> std::iterator and various container iterators?

std::iterator only defines a bunch of typedefs. It is basically an
er class; you can define an iterator without inheriting from it,
provided to provide the relevant nested typedefs.

The various iterators concepts are described in STL SGI:
http://www.sgi.com/tech/stl/Iterators.html
- InputIterators may be dereferenced for reading and can only be
incremented and a range cannot be used more than once.
- OutputIterators can be dereferenced for writing and can only be
incremented and a range cannot be used more than once.
- ForwardIterators guarantee that you can use a range more than once (by
example if you have an algorithm with more than one pass). But they can
only be increamented (like in a simple list).
- BidirectionalIterators are like the ForwardIterators but iterators can
be decremented (like in a double ended list).
- RandomIterators are like BidirectionalIterators but you can directly
access an iterator at a given distance from another iterator (typically
an array).

Michael