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: std::begin() and std::end() are supported
template <typename Range>
using is_range = cm::bool_constant<
  cm::is_iterator<decltype(std::begin(std::declval<const Range>()))>::value &&
  cm::is_iterator<decltype(std::end(std::declval<const Range>()))>::value>;

// checks if a type is an input range type: std::begin() and std::end() are
// 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::bool_constant<std::is_class<Range>::value ||
                    std::is_pointer<Range>::value ||
                    std::is_array<Range>::value>;
#else
  cm::bool_constant<cm::is_input_iterator<decltype(
                      std::begin(std::declval<const Range>()))>::value &&
                    cm::is_input_iterator<decltype(
                      std::end(std::declval<const Range>()))>::value>;
#endif

} // namespace cm

#endif