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Add mp_nth_element

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Peter Dimov
2017-10-15 16:56:22 +03:00
parent a5e74b2951
commit c14d6030c2
4 changed files with 124 additions and 0 deletions
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39
include/boost/mp11/algorithm.hpp
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@@ -508,6 +508,45 @@ template<template<class...> class L, class T1, class... T, template<class...> cl
template<class L, template<class...> class P> using mp_sort = typename detail::mp_sort_impl<L, P>::type;
// mp_nth_element(_c)<L, I, P>
namespace detail
{
template<class L, std::size_t I, template<class...> class P> struct mp_nth_element_impl;
template<template<class...> class L, class T1, std::size_t I, template<class...> class P> struct mp_nth_element_impl<L<T1>, I, P>
{
static_assert( I == 0, "mp_nth_element index out of range" );
using type = T1;
};
template<template<class...> class L, class T1, class... T, std::size_t I, template<class...> class P> struct mp_nth_element_impl<L<T1, T...>, I, P>
{
static_assert( I < 1 + sizeof...(T), "mp_nth_element index out of range" );
template<class U> using F = P<U, T1>;
using part = mp_partition<L<T...>, F>;
using L1 = mp_first<part>;
static std::size_t const N1 = mp_size<L1>::value;
using L2 = mp_second<part>;
using type = typename mp_cond<
mp_bool<(I < N1)>, mp_nth_element_impl<L1, I, P>,
mp_bool<(I == N1)>, mp_identity<T1>,
mp_true, mp_nth_element_impl<L2, I - N1 - 1, P>
>::type;
};
} // namespace detail
template<class L, std::size_t I, template<class...> class P> using mp_nth_element_c = typename detail::mp_nth_element_impl<L, I, P>::type;
template<class L, class I, template<class...> class P> using mp_nth_element = typename detail::mp_nth_element_impl<L, std::size_t{ I::value }, P>::type;
// mp_find<L, V>
namespace detail
{