Question

I see a public std::istream_iterator::_M_equal member function in my C++ implementation (it is used to compare istream iterators by other standard global functions). The standard does not require that member function to be available to the user.

I would like to know if implementations providing more public member functions other than those required by the standard can still be considered “standard”.

Answer 1

Yes, this is allowed by the standard.

The required interface is described by the standard document, but generally not the exact way to implement it. Names starting with underscore+uppercase letter, like _M_equal, are specifically reserved to the implementation.