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

   1 /*!
   2 @file
   3 Forward declares `boost::hana::count_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_COUNT_IF_HPP
  11 #define BOOST_HANA_FWD_COUNT_IF_HPP
  12
  13 #include <boost/hana/config.hpp>
  14 #include <boost/hana/core/when.hpp>
  15
  16
  17 BOOST_HANA_NAMESPACE_BEGIN
  18     //! Return the number of elements in the structure for which the
  19     //! `predicate` is satisfied.
  20     //! @ingroup group-Foldable
  21     //!
  22     //! Specifically, returns an object of an unsigned integral type, or
  23     //! a `Constant` holding such an object, which represents the number
  24     //! of elements in the structure satisfying the given `predicate`.
  25     //!
  26     //!
  27     //! @param xs
  28     //! The structure whose elements are counted.
  29     //!
  30     //! @param predicate
  31     //! A function called as `predicate(x)`, where `x` is an element of the
  32     //! structure, and returning a `Logical` representing whether `x` should
  33     //! be counted.
  34     //!
  35     //!
  36     //! Example
  37     //! -------
  38     //! @include example/count_if.cpp
  39 #ifdef BOOST_HANA_DOXYGEN_INVOKED
  40     constexpr auto count_if = [](auto&& xs, auto&& predicate) {
  41         return tag-dispatched;
  42     };
  43 #else
  44     template <typename T, typename = void>
  45     struct count_if_impl : count_if_impl<T, when<true>> { };
  46
  47     struct count_if_t {
  48         template <typename Xs, typename Pred>
  49         constexpr auto operator()(Xs&& xs, Pred&& pred) const;
  50     };
  51
  52     constexpr count_if_t count_if{};
  53 #endif
  54 BOOST_HANA_NAMESPACE_END
  55
  56 #endif // !BOOST_HANA_FWD_COUNT_IF_HPP