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Implement mp_rotate_right in terms of mp_rotate_left

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This commit is contained in:
Peter Dimov
2020-01-18 18:44:43 +02:00
parent d3f0738bf4
commit 8ef7658518
1 changed files with 6 additions and 21 deletions
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27
include/boost/mp11/algorithm.hpp
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@@ -1105,22 +1105,13 @@ using mp_starts_with = typename detail::mp_starts_with_impl<L1, L2>::type;
namespace detail
{
template<class L, std::size_t N> struct canonical_rotation
{
// provide a default rotation so that "no type named 'type'" errors appear in mp_rotate_impl instead of here
using type = mp_size_t<0>;
};
// limit divisor to 1 to avoid division by 0 and give a rotation of 0 for lists containing 0 or 1 elements
template<std::size_t Ln, std::size_t N> using canonical_left_rotation = mp_size_t<N % (Ln == 0? 1: Ln)>;
template<template<class...> class L, class... T, std::size_t N> struct canonical_rotation<L<T...>, N>
{
// limit divisor to 1 to avoid division by 0 and give a rotation of 0 for lists containing 0 or 1 elements
using type = mp_size_t<N % (sizeof...(T) == 0 ? 1 : sizeof...(T))>;
};
template<class L, std::size_t N> using canonical_rotation_t = typename canonical_rotation<L, N>::type;
// 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;
struct right_rotation;
template<class L, class N, class D> struct mp_rotate_impl
{
@@ -1139,19 +1130,13 @@ template<template<class...> class L, class... T, std::size_t N> struct mp_rotate
using type = mp_rename<mp_append<mp_drop_c<mp_list<T...>, N>, mp_take_c<mp_list<T...>, N>>, L>;
};
template<template<class...> class L, class... T, std::size_t N> struct mp_rotate_impl<L<T...>, mp_size_t<N>, right_rotation>
{
// perform right rotation as a left rotation by inverting the number of elements to rotate
using type = typename mp_rotate_impl<L<T...>, canonical_rotation_t<L<T...>, sizeof...(T) - N>, left_rotation>::type;
};
} // namespace detail
template<class L, std::size_t N> using mp_rotate_left_c = typename detail::mp_rotate_impl<L, detail::canonical_rotation_t<L, N>, detail::left_rotation>::type;
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, class N> using mp_rotate_left = mp_rotate_left_c<L, std::size_t{ N::value }>;
// mp_rotate_right(_c)<L, N>
template<class L, std::size_t N> using mp_rotate_right_c = typename detail::mp_rotate_impl<L, detail::canonical_rotation_t<L, N>, detail::right_rotation>::type;
template<class L, std::size_t N> using mp_rotate_right_c = mp_rotate_left<L, detail::canonical_right_rotation<mp_size<L>::value, N>>;
template<class L, class N> using mp_rotate_right = mp_rotate_right_c<L, std::size_t{ N::value }>;
// mp_min_element<L, P>