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Add mp_transform_first, second, third

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This commit is contained in:
Peter Dimov
2019-01-08 02:17:32 +02:00
parent 16c6f93cff
commit 7e501e3cc8
9 changed files with 367 additions and 3 deletions
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64
include/boost/mp11/list.hpp
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@@ -279,6 +279,70 @@ template<template<class...> class L, class U1, class U2, class U3, class... U, c
template<class L, class T> using mp_replace_third = typename detail::mp_replace_third_impl<L, T>::type;
// mp_transform_front<L, F>
namespace detail
{
template<class L, template<class...> class F> struct mp_transform_front_impl
{
// An error "no type named 'type'" here means that the first argument to mp_transform_front
// is either not a list, or is an empty list
};
template<template<class...> class L, class U1, class... U, template<class...> class F> struct mp_transform_front_impl<L<U1, U...>, F>
{
using type = L<F<U1>, U...>;
};
} // namespace detail
template<class L, template<class...> class F> using mp_transform_front = typename detail::mp_transform_front_impl<L, F>::type;
template<class L, class Q> using mp_transform_front_q = mp_transform_front<L, Q::template fn>;
// mp_transform_first<L, F>
template<class L, template<class...> class F> using mp_transform_first = typename detail::mp_transform_front_impl<L, F>::type;
template<class L, class Q> using mp_transform_first_q = mp_transform_first<L, Q::template fn>;
// mp_transform_second<L, F>
namespace detail
{
template<class L, template<class...> class F> struct mp_transform_second_impl
{
// An error "no type named 'type'" here means that the first argument to mp_transform_second
// is either not a list, or has fewer than two elements
};
template<template<class...> class L, class U1, class U2, class... U, template<class...> class F> struct mp_transform_second_impl<L<U1, U2, U...>, F>
{
using type = L<U1, F<U2>, U...>;
};
} // namespace detail
template<class L, template<class...> class F> using mp_transform_second = typename detail::mp_transform_second_impl<L, F>::type;
template<class L, class Q> using mp_transform_second_q = mp_transform_second<L, Q::template fn>;
// mp_transform_third<L, F>
namespace detail
{
template<class L, template<class...> class F> struct mp_transform_third_impl
{
// An error "no type named 'type'" here means that the first argument to mp_transform_third
// is either not a list, or has fewer than three elements
};
template<template<class...> class L, class U1, class U2, class U3, class... U, template<class...> class F> struct mp_transform_third_impl<L<U1, U2, U3, U...>, F>
{
using type = L<U1, U2, F<U3>, U...>;
};
} // namespace detail
template<class L, template<class...> class F> using mp_transform_third = typename detail::mp_transform_third_impl<L, F>::type;
template<class L, class Q> using mp_transform_third_q = mp_transform_third<L, Q::template fn>;
} // namespace mp11
} // namespace boost