projects / ceph.git / blame
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|---|---|---|
| 7c673cae FG |
1 | /*! |
| 2 | @file | |
| 3 | Forward declares `boost::hana::count_if`. | |
| 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_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 |