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 use SFINAE and replace bool by:

typename enable_if<
   is_same::iterator_category,
           std::forward_iterator_tag>::value,
   bool>::type

You may need to define is_same and enable_if yourself if you don't want to pull them from Boost or TR1:

template 
struct is_same { static const bool value = false; };

template 
struct is_same { static const bool value = true; };

template  struct enable_if { };
template  struct enable_if { typedef T type; };