Sprout/sprout/detail/algorithm/count_n_if.hpp

51 lines
1.8 KiB
C++

#ifndef SPROUT_DETAIL_ALGORITHM_COUNT_N_IF_HPP
#define SPROUT_DETAIL_ALGORITHM_COUNT_N_IF_HPP
#include <iterator>
#include <sprout/config.hpp>
#include <sprout/iterator/operation.hpp>
#include <sprout/algorithm/count_if.hpp>
namespace sprout {
namespace detail {
template<typename InputIterator, typename Size, typename Predicate>
inline SPROUT_CONSTEXPR typename std::iterator_traits<InputIterator>::difference_type
count_n_if(
InputIterator first, Size n, Predicate pred,
std::random_access_iterator_tag*
)
{
return sprout::count_if(first, sprout::next(first, n), pred);
}
template<typename InputIterator, typename Size, typename Predicate>
inline SPROUT_CONSTEXPR typename std::iterator_traits<InputIterator>::difference_type
count_n_if_impl(InputIterator first, Size n, Predicate pred) {
return n == 0 ? 0
: (pred(*first) ? 1 : 0) + sprout::detail::count_n_if(sprout::next(first), n - 1, pred)
;
}
template<typename InputIterator, typename Size, typename Predicate>
inline SPROUT_CONSTEXPR typename std::iterator_traits<InputIterator>::difference_type
count_n_if(
InputIterator first, Size n, Predicate pred,
void*
)
{
return sprout::detail::count_n_if_impl(first, n, pred);
}
//
// count_n_if
//
template<typename InputIterator, typename Size, typename Predicate>
inline SPROUT_CONSTEXPR typename std::iterator_traits<InputIterator>::difference_type
count_n_if(InputIterator first, Size n, Predicate pred) {
typedef typename std::iterator_traits<InputIterator>::iterator_category* category;
return sprout::detail::count_n_if(first, n, pred, category());
}
} // namespace detail
} // namespace sprout
#endif // #ifndef SPROUT_DETAIL_ALGORITHM_COUNT_N_IF_HPP