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]

the position indicated by the iterator rbegin()? (For arrays
as well as standard containers)

Typo. should be rend()

 

[Victor Bazarov]

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)

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

 

[Pete Becker]

Does it give similar guarantee about the position before the first
element
No.

the position indicated by the iterator rbegin()?

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

 

[Sumit Rajan]

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)

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.

 

[Neelesh Bodas]

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

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.

 

[Neelesh Bodas]

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.

Thanks Sumit, Just opened Josuttis' Book.