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

   1 /*!
   2 @file
   3 Defines `boost::hana::adjust_if`.
   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_ADJUST_IF_HPP
  11 #define BOOST_HANA_ADJUST_IF_HPP
  12
  13 #include <boost/hana/fwd/adjust_if.hpp>
  14
  15 #include <boost/hana/bool.hpp>
  16 #include <boost/hana/concept/functor.hpp>
  17 #include <boost/hana/config.hpp>
  18 #include <boost/hana/core/dispatch.hpp>
  19 #include <boost/hana/if.hpp>
  20 #include <boost/hana/transform.hpp>
  21
  22
  23 BOOST_HANA_NAMESPACE_BEGIN
  24     //! @cond
  25     template <typename Xs, typename Pred, typename F>
  26     constexpr auto adjust_if_t::operator()(Xs&& xs, Pred const& pred, F const& f) const {
  27         using S = typename hana::tag_of<Xs>::type;
  28         using AdjustIf = BOOST_HANA_DISPATCH_IF(adjust_if_impl<S>,
  29             hana::Functor<S>::value
  30         );
  31
  32     #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
  33         static_assert(hana::Functor<S>::value,
  34         "hana::adjust_if(xs, pred, f) requires 'xs' to be a Functor");
  35     #endif
  36
  37         return AdjustIf::apply(static_cast<Xs&&>(xs), pred, f);
  38     }
  39     //! @endcond
  40
  41     namespace detail {
  42         template <typename Pred, typename F>
  43         struct apply_if {
  44             Pred const& pred;
  45             F const& f;
  46
  47             template <typename X>
  48             constexpr decltype(auto) helper(bool cond, X&& x) const
  49             { return cond ? f(static_cast<X&&>(x)) : static_cast<X&&>(x); }
  50
  51             template <typename X>
  52             constexpr decltype(auto) helper(hana::true_, X&& x) const
  53             { return f(static_cast<X&&>(x)); }
  54
  55             template <typename X>
  56             constexpr decltype(auto) helper(hana::false_, X&& x) const
  57             { return static_cast<X&&>(x); }
  58
  59
  60             template <typename X>
  61             constexpr decltype(auto) operator()(X&& x) const {
  62                 auto cond = hana::if_(pred(x), hana::true_c, hana::false_c);
  63                 return this->helper(cond, static_cast<X&&>(x));
  64             }
  65         };
  66     }
  67
  68     template <typename Fun, bool condition>
  69     struct adjust_if_impl<Fun, when<condition>> : default_ {
  70         template <typename Xs, typename Pred, typename F>
  71         static constexpr auto apply(Xs&& xs, Pred const& pred, F const& f) {
  72             return hana::transform(static_cast<Xs&&>(xs),
  73                                    detail::apply_if<Pred, F>{pred, f});
  74         }
  75     };
  76 BOOST_HANA_NAMESPACE_END
  77
  78 #endif // !BOOST_HANA_ADJUST_IF_HPP