How to restrict an iterator to being a forward iterator?

Question

I have a function that needs to enumerate an iterator multiple times, but according to MSDN, \"Once you increment any copy of an input iterator, none of the other copies can

Answer 1

You can do this using std::enable_if:

#include 
#include 
#include 

template 
typename std::enable_if::iterator_category>::value,
                    bool>::type
EnumerateTwice(It begin, It end, TCallback) {
    ...
}

This uses class from C++11 but all of this can be done in C++03 as well.