projects / ceph.git / blame
| Commit | Line | Data |
|---|---|---|
| 7c673cae FG |
1 | /*! |
| 2 | @file | |
| 3 | Forward declares `boost::hana::count`. | |
| 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_COUNT_HPP | |
| 11 | #define BOOST_HANA_FWD_COUNT_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 that compare equal to | |
| 19 | //! a given value. | |
| 20 | //! @ingroup group-Foldable | |
| 21 | //! | |
| 22 | //! Given a Foldable structure `xs` and a value `value`, `count` returns | |
| 23 | //! an unsigned integral, or a Constant thereof, representing the number | |
| 24 | //! of elements of `xs` that compare equal to `value`. For this method to | |
| 25 | //! be well-defined, all the elements of the structure must be Comparable | |
| 26 | //! with the given value. | |
| 27 | //! | |
| 28 | //! | |
| 29 | //! @param xs | |
| 30 | //! The structure whose elements are counted. | |
| 31 | //! | |
| 32 | //! @param value | |
| 33 | //! A value compared with each element in the structure. Elements | |
| 34 | //! that compare equal to this value are counted, others are not. | |
| 35 | //! | |
| 36 | //! | |
| 37 | //! Example | |
| 38 | //! ------- | |
| 39 | //! @include example/count.cpp | |
| 40 | #ifdef BOOST_HANA_DOXYGEN_INVOKED | |
| 41 | constexpr auto count = [](auto&& xs, auto&& value) { | |
| 42 | return tag-dispatched; | |
| 43 | }; | |
| 44 | #else | |
| 45 | template <typename T, typename = void> | |
| 46 | struct count_impl : count_impl<T, when<true>> { }; | |
| 47 | ||
| 48 | struct count_t { | |
| 49 | template <typename Xs, typename Value> | |
| 50 | constexpr auto operator()(Xs&& xs, Value&& value) const; | |
| 51 | }; | |
| 52 | ||
| 53 | constexpr count_t count{}; | |
| 54 | #endif | |
| 55 | BOOST_HANA_NAMESPACE_END | |
| 56 | ||
| 57 | #endif // !BOOST_HANA_FWD_COUNT_HPP |