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/*!
@file
Forward declares `boost::hana::find`.
Copyright Louis Dionne 2013-2022
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_HPP
#define BOOST_HANA_FWD_FIND_HPP
#include <boost/hana/config.hpp>
#include <boost/hana/core/when.hpp>
namespace boost { namespace hana {
//! Finds the value associated to the given key in a structure.
//! @ingroup group-Searchable
//!
//! Given a `key` and a `Searchable` structure, `find` returns the `just`
//! the first value whose key is equal to the given `key`, or `nothing` if
//! there is no such key. Comparison is done with `equal`. `find` satisfies
//! the following:
//! @code
//! find(xs, key) == find_if(xs, equal.to(key))
//! @endcode
//!
//!
//! @param xs
//! The structure to be searched.
//!
//! @param key
//! A key to be searched for in the structure. The key has to be
//! `Comparable` with the other keys of the structure. In the current
//! version of the library, the comparison of `key` with any other key
//! of the structure must return a compile-time `Logical`.
//!
//!
//! Example
//! -------
//! @include example/find.cpp
#ifdef BOOST_HANA_DOXYGEN_INVOKED
constexpr auto find = [](auto&& xs, auto const& key) {
return tag-dispatched;
};
#else
template <typename S, typename = void>
struct find_impl : find_impl<S, when<true>> { };
struct find_t {
template <typename Xs, typename Key>
constexpr auto operator()(Xs&& xs, Key const& key) const;
};
BOOST_HANA_INLINE_VARIABLE constexpr find_t find{};
#endif
}} // end namespace boost::hana
#endif // !BOOST_HANA_FWD_FIND_HPP
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