why does std::for_each iterator need a copy constructable iterator

I noticed that std::for_each requires it's iterators to meet the requirement InputIterator, which in turn requires Iterator and then Copy{Contructable,Assignable}.

That's not the only thing, std::for_each actually uses the copy constructor (cc) (not assignment as far as my configuration goes). That is, deleting the cc from the iterator will result in:

error: use of deleted function ‘some_iterator::some_iterator(const some_iterator&)’

Why does std::for_each need a cc? I found this particularly inconvenient, since I created an iterator which recursively iterates through files in a folder, keeping track of the files and folders on a queue. This means that the iterator has a queue data member, which would also have to be copied if the cc is used: that is unnecessarily inefficient.

The strange thing is that the cc is not called in this simple example:

#include <iostream>
#include <iterator>
#include <algorithm>


class infinite_5_iterator
:
public std::iterator<std::input_iterator_tag, int>
{
public:
  infinite_5_iterator() = default;
  infinite_5_iterator(infinite_5_iterator const &) {std::cout << "copy constr "; }

  infinite_5_iterator &operator=(infinite_5_iterator const &) = delete;


  int operator*() { return 5; }
  infinite_5_iterator &operator++() { return *this; }
  bool operator==(infinite_5_iterator const &) const { return false; }
  bool operator!=(infinite_5_iterator const &) const { return true; }
};

int main() {
  std::for_each(infinite_5_iterator(), infinite_5_iterator(),
    [](int v) {
      std::cout << v << ' ';
    }
  );
}

source: http://ift.tt/1F3JZzX

It however is needed compile time. Why does std::for_each need to copy construct the iterator, and when is this done? Isn't this extremely inefficient?

NOTE: I'm talking about the cc of the iterator, not of it's elements, as is done here: unexpected copies with foreach over a map