ceph/src/boost/boost/hana/fwd/find_if.hpp

   1 /*!
   2 @file
   3 Forward declares `boost::hana::find_if`.
   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_FWD_FIND_IF_HPP
  11 #define BOOST_HANA_FWD_FIND_IF_HPP
  12
  13 #include <boost/hana/config.hpp>
  14 #include <boost/hana/core/when.hpp>
  15
  16
  17 BOOST_HANA_NAMESPACE_BEGIN
  18     //! Finds the value associated to the first key satisfying a predicate.
  19     //! @ingroup group-Searchable
  20     //!
  21     //! Given a `Searchable` structure `xs` and a predicate `pred`,
  22     //! `find_if(xs, pred)` returns `just` the first element whose key
  23     //! satisfies the predicate, or `nothing` if there is no such element.
  24     //!
  25     //!
  26     //! @param xs
  27     //! The structure to be searched.
  28     //!
  29     //! @param predicate
  30     //! A function called as `predicate(k)`, where `k` is a key of the
  31     //! structure, and returning whether `k` is the key of the element
  32     //! being searched for. In the current version of the library, the
  33     //! predicate has to return an `IntegralConstant` holding a value
  34     //! that can be converted to `bool`.
  35     //!
  36     //!
  37     //! Example
  38     //! -------
  39     //! @include example/find_if.cpp
  40 #ifdef BOOST_HANA_DOXYGEN_INVOKED
  41     constexpr auto find_if = [](auto&& xs, auto&& predicate) {
  42         return tag-dispatched;
  43     };
  44 #else
  45     template <typename S, typename = void>
  46     struct find_if_impl : find_if_impl<S, when<true>> { };
  47
  48     struct find_if_t {
  49         template <typename Xs, typename Pred>
  50         constexpr auto operator()(Xs&& xs, Pred&& pred) const;
  51     };
  52
  53     constexpr find_if_t find_if{};
  54 #endif
  55 BOOST_HANA_NAMESPACE_END
  56
  57 #endif // !BOOST_HANA_FWD_FIND_IF_HPP