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/*!
@file
Forward declares `boost::hana::find_if`.
@copyright Louis Dionne 2013-2016
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
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