iterator beyond the first element

[Neelesh Bodas]

C++ guarantees that there exists a valid iterator beyond the last
element of a container. However, such iterator might not be written or
dereferenced. This is also true for arrays - C++ gurantees that there
exists one position available beyond the end of array.

Does it give similar guarantee about the position before the first
element - the position indicated by the iterator rbegin()? (For arrays
as well as standard containers)

[Neelesh Bodas]

Re: iterator beyond the first element


Neelesh Bodas wrote:[color=blue]
> the position indicated by the iterator rbegin()? (For arrays
> as well as standard containers)[/color]

Typo. should be rend()

[Pete Becker]

Re: iterator beyond the first element

Neelesh Bodas wrote:[color=blue]
>
> Does it give similar guarantee about the position before the first
> element[/color]

No.
[color=blue]
> the position indicated by the iterator rbegin()?[/color]

rbegin() is completely different. Reverse iterators for containers use
the end() and begin() iterators and index one off from the iterator's
position.

--

Pete Becker
Dinkumware, Ltd. (http://www.dinkumware.com)

[Sumit Rajan]

Re: iterator beyond the first element


"Neelesh Bodas" <neelesh.bodas@ gmail.com> wrote in message
news:1133188428 .317619.131460@ f14g2000cwb.goo glegroups.com.. .[color=blue]
> C++ guarantees that there exists a valid iterator beyond the last
> element of a container. However, such iterator might not be written or
> dereferenced. This is also true for arrays - C++ gurantees that there
> exists one position available beyond the end of array.
>
> Does it give similar guarantee about the position before the first
> element - the position indicated by the iterator rbegin()? (For arrays
> as well as standard containers)[/color]


If you have a copy of "The C++ Standard Library" close to you, please take a
look at Section 7.4.1. You will find a detailed explanation on this.


Regards,
Sumit.
--
Sumit Rajan <sumitr@msdc.hc ltech.com>

[Neelesh Bodas]

Re: iterator beyond the first element


Pete Becker wrote:[color=blue]
> rbegin() is completely different. Reverse iterators for containers use
> the end() and begin() iterators and index one off from the iterator's
> position.[/color]

Yeah, that was a typo. And yes, I get what you are saying - you mean to
say that the logical position and physical position of reverse
iterators are different - they are one unit off - Is that right? If so,
My confusion is resolved.

[Victor Bazarov]

Re: iterator beyond the first element

Neelesh Bodas wrote:[color=blue]
> C++ guarantees that there exists a valid iterator beyond the last
> element of a container. However, such iterator might not be written or
> dereferenced. This is also true for arrays - C++ gurantees that there
> exists one position available beyond the end of array.
>
> Does it give similar guarantee about the position before the first
> element - the position indicated by the iterator rbegin()? (For arrays
> as well as standard containers)[/color]

You are mistaken about at least one thing: 'rbegin()' returns an iterator
that points to the _last_ element, not first.

No, C++ does not guarantee the existence of "one-before-first" iterator
(in your terms it would be '--begin()').

V

[Neelesh Bodas]

Re: iterator beyond the first element

Sumit Rajan wrote:[color=blue]
> If you have a copy of "The C++ Standard Library" close to you, please take a
> look at Section 7.4.1. You will find a detailed explanation on this.[/color]

Thanks Sumit, Just opened Josuttis' Book. :-)