63e88f80
 Hu Chunming
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/*!
@file
Defines `boost::hana::fill`.
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_FILL_HPP
#define BOOST_HANA_FILL_HPP
#include <boost/hana/fwd/fill.hpp>
#include <boost/hana/concept/functor.hpp>
#include <boost/hana/concept/sequence.hpp>
#include <boost/hana/config.hpp>
#include <boost/hana/core/dispatch.hpp>
#include <boost/hana/core/make.hpp>
#include <boost/hana/functional/always.hpp>
#include <boost/hana/transform.hpp>
#include <boost/hana/unpack.hpp>
namespace boost { namespace hana {
//! @cond
template <typename Xs, typename Value>
constexpr auto fill_t::operator()(Xs&& xs, Value&& value) const {
using S = typename hana::tag_of<Xs>::type;
using Fill = BOOST_HANA_DISPATCH_IF(fill_impl<S>,
hana::Functor<S>::value
);
#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
static_assert(hana::Functor<S>::value,
"hana::fill(xs, value) requires 'xs' to be a Functor");
#endif
return Fill::apply(static_cast<Xs&&>(xs),
static_cast<Value&&>(value));
}
//! @endcond
template <typename Fun, bool condition>
struct fill_impl<Fun, when<condition>> : default_ {
template <typename Xs, typename Value>
static constexpr auto apply(Xs&& xs, Value&& v) {
return hana::transform(static_cast<Xs&&>(xs),
hana::always(static_cast<Value&&>(v))
);
}
};
template <typename S>
struct fill_impl<S, when<Sequence<S>::value>> {
//! @cond
template <typename V>
struct filler {
V const& v;
template <typename ...Xs>
constexpr auto operator()(Xs const& ...xs) const {
return hana::make<S>(((void)xs, v)...);
}
};
//! @endcond
template <typename Xs, typename V>
static constexpr auto apply(Xs const& xs, V const& v) {
return hana::unpack(xs, filler<V>{v});
}
};
}} // end namespace boost::hana
#endif // !BOOST_HANA_FILL_HPP
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