iter_difference_t.hpp

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//
// Created by cosge on 2023-12-03.
//
 
#ifndef VCCC_ITERATOR_ITER_DIFFERENCE_T_HPP_
#define VCCC_ITERATOR_ITER_DIFFERENCE_T_HPP_
 
#include "vccc/__iterator/incrementable_traits.hpp"
#include "vccc/__iterator/iterator_traits/forward_declare.hpp"
#include "vccc/__type_traits/has_typename_difference_type.hpp"
#include "vccc/__type_traits/remove_cvref.hpp"
 
namespace vccc {
namespace detail {
 
template<
    typename T,
    bool = is_primary_iterator_traits< cxx20_iterator_traits< remove_cvref_t<T> > >::value,
    bool = has_typename_difference_type<incrementable_traits<remove_cvref_t<T>>>::value
>
struct iter_difference_impl {};
 
template<typename T, bool v>
struct iter_difference_impl<T, false, v> {
  using type = typename cxx20_iterator_traits<remove_cvref_t<T>>::difference_type;
};
 
template<typename T>
struct iter_difference_impl<T, true, true> {
  using type = typename incrementable_traits<remove_cvref_t<T>>::difference_type;
};
 
} // namespace detail
 
 
template<typename T>
struct iter_difference : detail::iter_difference_impl<T> {};
 
template<typename T>
using iter_difference_t = typename iter_difference<T>::type;
 
 
} // namespace vccc
 
#endif // VCCC_ITERATOR_ITER_DIFFERENCE_T_HPP_