The iterator library that is part of the C++ Standard Library provides the following helpers for writing generic code:
All the functions above are defined in the <iterator> header. It’s always preferable to use these generic functions when writing the generic code instead of using equivalent member functions of the containers.
Functions from (1) to (8) are defined for built-in arrays and for every type that provides members begin() and end(). Note, that std::cbegin() requires the definition of the constant version of member function c.begin().
Functions for (9) to (12): std::prev() and std::next() are generic functions to increment or decrement the iterator by the specified number of hops (by default, 1), function std::distance() is a generic function to calculate the number of hops between the specified pair of iterators and function std::advance() is a generic equivalent of the operator +=.
Please note, if either the argument of std::next() and std::advance() is negative or the argument of std::prev() is positive then the specified iterator must be bidirectional iterator (see Categories of Iterators in C++).