Utilities/std/cmext/iterator

// -*-c++-*-
// vim: set ft=cpp:

/* Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
   file Copyright.txt or https://cmake.org/licensing for details.  */
#ifndef cmext_iterator
#define cmext_iterator

#include <iterator>

#include <cm/type_traits>

namespace cm {

// checks if a type is an iterator type
template <typename I>
using is_iterator =
  std::is_integral<typename std::iterator_traits<I>::difference_type>;

// checks if a type is an input iterator type
template <typename I>
using is_input_iterator =
  std::is_base_of<std::input_iterator_tag,
                  typename std::iterator_traits<I>::iterator_category>;

// checks if a type is a range type: must have a difference_type type
template <typename Range>
using is_range = cm::bool_constant<
  cm::is_iterator<decltype(std::declval<const Range>().begin())>::value &&
  cm::is_iterator<decltype(std::declval<const Range>().end())>::value>;

// checks if a type is an input range type: must have methods begin() and end()
// returning an input iterator
template <typename Range>
using is_input_range =
#if defined(_MSC_VER) && _MSC_VER < 1920
  // MS C++ is not able to evaluate complex type introspection,
  // so use a simplified version
  cm::is_input_iterator<typename Range::const_iterator>;
#else
  cm::bool_constant<
    cm::is_input_iterator<decltype(
      std::declval<const Range>().begin())>::value &&
    cm::is_input_iterator<decltype(std::declval<const Range>().end())>::value>;
#endif

} // namespace cm

#endif