boost/hana/contains.hpp

   1 /*!
   2 @file
   3 Defines `boost::hana::contains` and `boost::hana::in`.
   4
   5 @copyright Louis Dionne 2013-2017
   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_CONTAINS_HPP
  11 #define BOOST_HANA_CONTAINS_HPP
  12
  13 #include <boost/hana/fwd/contains.hpp>
  14
  15 #include <boost/hana/any_of.hpp>
  16 #include <boost/hana/concept/searchable.hpp>
  17 #include <boost/hana/config.hpp>
  18 #include <boost/hana/core/dispatch.hpp>
  19 #include <boost/hana/equal.hpp>
  20
  21
  22 BOOST_HANA_NAMESPACE_BEGIN
  23     //! @cond
  24     template <typename Xs, typename Key>
  25     constexpr auto contains_t::operator()(Xs&& xs, Key&& key) const {
  26         using S = typename hana::tag_of<Xs>::type;
  27         using Contains = BOOST_HANA_DISPATCH_IF(contains_impl<S>,
  28             hana::Searchable<S>::value
  29         );
  30
  31     #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
  32         static_assert(hana::Searchable<S>::value,
  33         "hana::contains(xs, key) requires 'xs' to be a Searchable");
  34     #endif
  35
  36         return Contains::apply(static_cast<Xs&&>(xs),
  37                                static_cast<Key&&>(key));
  38     }
  39     //! @endcond
  40
  41     template <typename S, bool condition>
  42     struct contains_impl<S, when<condition>> : default_ {
  43         template <typename Xs, typename X>
  44         static constexpr auto apply(Xs&& xs, X&& x) {
  45             return hana::any_of(static_cast<Xs&&>(xs),
  46                     hana::equal.to(static_cast<X&&>(x)));
  47         }
  48     };
  49 BOOST_HANA_NAMESPACE_END
  50
  51 #endif // !BOOST_HANA_CONTAINS_HPP