ceph/src/boost/libs/hana/include/boost/hana/fwd/contains.hpp

   1 /*!
   2 @file
   3 Forward declares `boost::hana::contains` and `boost::hana::in`.
   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_FWD_CONTAINS_HPP
  11 #define BOOST_HANA_FWD_CONTAINS_HPP
  12
  13 #include <boost/hana/config.hpp>
  14 #include <boost/hana/core/when.hpp>
  15 #include <boost/hana/functional/flip.hpp>
  16 #include <boost/hana/functional/infix.hpp>
  17
  18
  19 BOOST_HANA_NAMESPACE_BEGIN
  20     //! Returns whether the key occurs in the structure.
  21     //! @ingroup group-Searchable
  22     //!
  23     //! Given a `Searchable` structure `xs` and a `key`, `contains` returns
  24     //! whether any of the keys of the structure is equal to the given `key`.
  25     //! If the structure is not finite, an equal key has to appear at a finite
  26     //! position in the structure for this method to finish. For convenience,
  27     //! `contains` can also be applied in infix notation.
  28     //!
  29     //!
  30     //! @param xs
  31     //! The structure to search.
  32     //!
  33     //! @param key
  34     //! A key to be searched for in the structure. The key has to be
  35     //! `Comparable` with the other keys of the structure.
  36     //!
  37     //!
  38     //! Example
  39     //! -------
  40     //! @include example/contains.cpp
  41 #ifdef BOOST_HANA_DOXYGEN_INVOKED
  42     constexpr auto contains = [](auto&& xs, auto&& key) {
  43         return tag-dispatched;
  44     };
  45 #else
  46     template <typename S, typename = void>
  47     struct contains_impl : contains_impl<S, when<true>> { };
  48
  49     struct contains_t {
  50         template <typename Xs, typename Key>
  51         constexpr auto operator()(Xs&& xs, Key&& key) const;
  52     };
  53
  54     constexpr auto contains = hana::infix(contains_t{});
  55 #endif
  56
  57     //! Return whether the key occurs in the structure.
  58     //! @ingroup group-Searchable
  59     //!
  60     //! Specifically, this is equivalent to `contains`, except `in` takes its
  61     //! arguments in reverse order. Like `contains`, `in` can also be applied
  62     //! in infix notation for increased expressiveness. This function is not a
  63     //! method that can be overriden; it is just a convenience function
  64     //! provided with the concept.
  65     //!
  66     //!
  67     //! Example
  68     //! -------
  69     //! @include example/in.cpp
  70     constexpr auto in = hana::infix(hana::flip(hana::contains));
  71 BOOST_HANA_NAMESPACE_END
  72
  73 #endif // !BOOST_HANA_FWD_CONTAINS_HPP