Caching the end iterator - Good idea or Bad Idea?

Question

Generally speaking is it a good idea to cache an end iterator (specifically STL containers) for efficiency and speed purposes? such as in the following bit of code:

Answer 1

The invalidation rules (for iterators) is defined very explicitly for each type of container. I find the SGI site very useful http://www.sgi.com/tech/stl/table_of_contents.html

Specifically for vectors I find:

[5] A vector's iterators are invalidated when its memory is reallocated. Additionally, inserting or deleting an element in the middle of a vector invalidates all iterators that point to elements following the insertion or deletion point. It follows that you can prevent a vector's iterators from being invalidated if you use reserve() to preallocate as much memory as the vector will ever use, and if all insertions and deletions are at the vector's end.