/*!
@file
Forward declares `boost::hana::any_of`.

@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_ANY_OF_HPP
#define BOOST_HANA_FWD_ANY_OF_HPP

#include <boost/hana/config.hpp>
#include <boost/hana/core/when.hpp>


namespace boost { namespace hana {
    //! Returns whether any key of the structure satisfies the `predicate`.
    //! @ingroup group-Searchable
    //!
    //! If the structure is not finite, `predicate` has to be satisfied
    //! after looking at a finite number of keys for this method to finish.
    //!
    //!
    //! @param xs
    //! The structure to search.
    //!
    //! @param predicate
    //! A function called as `predicate(k)`, where `k` is a key of the
    //! structure, and returning a `Logical`.
    //!
    //!
    //! Example
    //! -------
    //! @include example/any_of.cpp
#ifdef BOOST_HANA_DOXYGEN_INVOKED
    constexpr auto any_of = [](auto&& xs, auto&& predicate) {
        return tag-dispatched;
    };
#else
    template <typename S, typename = void>
    struct any_of_impl : any_of_impl<S, when<true>> { };

    struct any_of_t {
        template <typename Xs, typename Pred>
        constexpr auto operator()(Xs&& xs, Pred&& pred) const;
    };

    BOOST_HANA_INLINE_VARIABLE constexpr any_of_t any_of{};
#endif
}} // end namespace boost::hana

#endif // !BOOST_HANA_FWD_ANY_OF_HPP
