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Simplify mp_rotate_impl

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Peter Dimov
2020-01-18 20:15:05 +02:00
parent 8ef7658518
commit 4e177f73ae
1 changed files with 3 additions and 19 deletions
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22
include/boost/mp11/algorithm.hpp
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@@ -1111,28 +1111,12 @@ template<std::size_t Ln, std::size_t N> using canonical_left_rotation = mp_size_
// perform right rotation as a left rotation by inverting the number of elements to rotate
template<std::size_t Ln, std::size_t N> using canonical_right_rotation = mp_size_t<Ln - N % (Ln == 0? 1: Ln)>;
struct left_rotation;
template<class L, class N, class D> struct mp_rotate_impl
{
// An error "no type named 'type'" here means that the first argument to mp_rotate_left/mp_rotate_right is not a list
};
template<template<class...> class L, class... T> struct mp_rotate_impl<L<T...>, mp_size_t<0>, left_rotation>
{
// fast-track the case of an identity rotation
using type = L<T...>;
};
template<template<class...> class L, class... T, std::size_t N> struct mp_rotate_impl<L<T...>, mp_size_t<N>, left_rotation>
{
// avoid errors when rotating fixed-sized lists by using mp_list for the transformation
using type = mp_rename<mp_append<mp_drop_c<mp_list<T...>, N>, mp_take_c<mp_list<T...>, N>>, L>;
};
// avoid errors when rotating fixed-sized lists by using mp_list for the transformation
template<class L, class N, class L2 = mp_rename<L, mp_list>> using mp_rotate_impl = mp_assign<L, mp_append< mp_drop<L2, N>, mp_take<L2, N> >>;
} // namespace detail
template<class L, std::size_t N> using mp_rotate_left_c = typename detail::mp_rotate_impl<L, detail::canonical_left_rotation<mp_size<L>::value, N>, detail::left_rotation>::type;
template<class L, std::size_t N> using mp_rotate_left_c = detail::mp_rotate_impl<L, detail::canonical_left_rotation<mp_size<L>::value, N>>;
template<class L, class N> using mp_rotate_left = mp_rotate_left_c<L, std::size_t{ N::value }>;
// mp_rotate_right(_c)<L, N>