update sources to v12.2.3

[ceph.git] / ceph / src / boost / boost / hana / fwd / find_if.hpp

diff --git a/ceph/src/boost/boost/hana/fwd/find_if.hpp b/ceph/src/boost/boost/hana/fwd/find_if.hpp
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+/*!
+@file
+Forward declares `boost::hana::find_if`.
+
+@copyright Louis Dionne 2013-2017
+Distributed under the Boost Software License, Version 1.0.
+(See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)
+ */
+
+#ifndef BOOST_HANA_FWD_FIND_IF_HPP
+#define BOOST_HANA_FWD_FIND_IF_HPP
+
+#include <boost/hana/config.hpp>
+#include <boost/hana/core/when.hpp>
+
+
+BOOST_HANA_NAMESPACE_BEGIN
+    //! Finds the value associated to the first key satisfying a predicate.
+    //! @ingroup group-Searchable
+    //!
+    //! Given a `Searchable` structure `xs` and a predicate `pred`,
+    //! `find_if(xs, pred)` returns `just` the first element whose key
+    //! satisfies the predicate, or `nothing` if there is no such element.
+    //!
+    //!
+    //! @param xs
+    //! The structure to be searched.
+    //!
+    //! @param predicate
+    //! A function called as `predicate(k)`, where `k` is a key of the
+    //! structure, and returning whether `k` is the key of the element
+    //! being searched for. In the current version of the library, the
+    //! predicate has to return an `IntegralConstant` holding a value
+    //! that can be converted to `bool`.
+    //!
+    //!
+    //! Example
+    //! -------
+    //! @include example/find_if.cpp
+#ifdef BOOST_HANA_DOXYGEN_INVOKED
+    constexpr auto find_if = [](auto&& xs, auto&& predicate) {
+        return tag-dispatched;
+    };
+#else
+    template <typename S, typename = void>
+    struct find_if_impl : find_if_impl<S, when<true>> { };
+
+    struct find_if_t {
+        template <typename Xs, typename Pred>
+        constexpr auto operator()(Xs&& xs, Pred&& pred) const;
+    };
+
+    constexpr find_if_t find_if{};
+#endif
+BOOST_HANA_NAMESPACE_END
+
+#endif // !BOOST_HANA_FWD_FIND_IF_HPP