ceph/src/boost/libs/hana/include/boost/hana/ap.hpp

   1 /*!
   2 @file
   3 Defines `boost::hana::ap`.
   4
   5 @copyright Louis Dionne 2013-2016
   6 Distributed under the Boost Software License, Version 1.0.
   7 (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
   8  */
   9
  10 #ifndef BOOST_HANA_AP_HPP
  11 #define BOOST_HANA_AP_HPP
  12
  13 #include <boost/hana/fwd/ap.hpp>
  14
  15 #include <boost/hana/chain.hpp>
  16 #include <boost/hana/concept/applicative.hpp>
  17 #include <boost/hana/concept/sequence.hpp>
  18 #include <boost/hana/config.hpp>
  19 #include <boost/hana/core/dispatch.hpp>
  20 #include <boost/hana/detail/variadic/foldl1.hpp>
  21 #include <boost/hana/functional/curry.hpp>
  22 #include <boost/hana/functional/partial.hpp>
  23 #include <boost/hana/transform.hpp>
  24
  25
  26 BOOST_HANA_NAMESPACE_BEGIN
  27     template <typename A, bool condition>
  28     struct ap_impl<A, when<condition>> : default_ {
  29         template <typename ...Args>
  30         static constexpr auto apply(Args&& ...args) = delete;
  31     };
  32
  33     //! @cond
  34     template <typename F, typename X>
  35     constexpr decltype(auto) ap_t::operator()(F&& f, X&& x) const {
  36         using Function = typename hana::tag_of<F>::type;
  37         using Value = typename hana::tag_of<X>::type;
  38         using Ap = BOOST_HANA_DISPATCH_IF(ap_impl<Function>,
  39             hana::Applicative<Function>::value && hana::Applicative<Value>::value
  40         );
  41
  42     #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
  43         static_assert(hana::Applicative<Function>::value,
  44         "hana::ap(f, x) requires 'f' to be an Applicative");
  45
  46         static_assert(hana::Applicative<Value>::value,
  47         "hana::ap(f, x) requires 'x' to be an Applicative");
  48     #endif
  49
  50         return Ap::apply(static_cast<F&&>(f), static_cast<X&&>(x));
  51     }
  52
  53     template <typename F, typename ...Xs>
  54     constexpr decltype(auto) ap_t::operator()(F&& f, Xs&& ...xs) const {
  55         static_assert(sizeof...(xs) >= 1,
  56         "hana::ap must be called with at least two arguments");
  57
  58         return detail::variadic::foldl1(
  59             *this,
  60             hana::transform(static_cast<F&&>(f), hana::curry<sizeof...(xs)>),
  61             static_cast<Xs&&>(xs)...
  62         );
  63     }
  64     //! @endcond
  65
  66     template <typename S>
  67     struct ap_impl<S, when<Sequence<S>::value>> {
  68         template <typename F, typename X>
  69         static constexpr decltype(auto) apply(F&& f, X&& x) {
  70             return hana::chain(
  71                 static_cast<F&&>(f),
  72                 hana::partial(hana::transform, static_cast<X&&>(x))
  73             );
  74         }
  75     };
  76 BOOST_HANA_NAMESPACE_END
  77
  78 #endif // !BOOST_HANA_AP_HPP