If Iterator is a random access iterator, then
std::iterator_traits<Iterator>::iterator_category
will be std::random_access_iterator_tag. The cleanest way to implement this is probably to create a second function template and have Foo call it:
template <typename Iterator>
void FooImpl(Iterator first, Iterator last, std::random_access_iterator_tag) {
// ...
}
template <typename Iterator>
void Foo(Iterator first, Iterator last) {
typedef typename std::iterator_traits<Iterator>::iterator_category category;
return FooImpl(first, last, category());
}
This has the advantage that you can overload FooImpl for different categories of iterators if you’d like.
Scott Meyers discusses this technique in one of the Effective C++ books (I don’t remember which one).