I need a function template that accepts two iterators that could be pointers. If the two arguments are random_access iterators I want the return type to be an object of

std::iterator<random_access_iterator_tag, ...> type

else a

std::iterator<bidirectional_iterator_tag, ...> type.

I also want the code to refuse compilation if the arguments are neither a bidirectional iterator, nor a pointer. I cannot have dependency on third party libraries e.g. Boost

Could you help me with the signature of this function so that it accepts bidirectional iterators as well as pointers, but not say input_iterator, output_iterator, forward_iterators.

One partial solution I can think of is the following

template<class T>
T foo( T iter1, T iter2) {
  const T tmp1 = reverse_iterator<T>(iter1);
  const T tmp2 = reverse_iterator<T>(iter2);
  // do something
}

The idea is that if it is not bidirectional the compiler will not let me construct a reverse_iterator from it.