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/*!
@file
Defines `boost::hana::count`.
@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_COUNT_HPP
#define BOOST_HANA_COUNT_HPP
#include <boost/hana/fwd/count.hpp>
#include <boost/hana/concept/foldable.hpp>
#include <boost/hana/config.hpp>
#include <boost/hana/core/dispatch.hpp>
#include <boost/hana/count_if.hpp>
#include <boost/hana/equal.hpp>
BOOST_HANA_NAMESPACE_BEGIN
//! @cond
template <typename Xs, typename Value>
constexpr auto count_t::operator()(Xs&& xs, Value&& value) const {
using S = typename hana::tag_of<Xs>::type;
using Count = BOOST_HANA_DISPATCH_IF(count_impl<S>,
hana::Foldable<S>::value
);
#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
static_assert(hana::Foldable<S>::value,
"hana::count(xs, value) requires 'xs' to be Foldable");
#endif
return Count::apply(static_cast<Xs&&>(xs), static_cast<Value&&>(value));
}
//! @endcond
template <typename T, bool condition>
struct count_impl<T, when<condition>> : default_ {
template <typename Xs, typename Value>
static constexpr auto apply(Xs&& xs, Value&& value) {
return hana::count_if(static_cast<Xs&&>(xs),
hana::equal.to(static_cast<Value&&>(value)));
}
};
BOOST_HANA_NAMESPACE_END
#endif // !BOOST_HANA_COUNT_HPP
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