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 Hu Chunming
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/*!
@file
Defines `boost::hana::adjust_if`.
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_ADJUST_IF_HPP
#define BOOST_HANA_ADJUST_IF_HPP
#include <boost/hana/fwd/adjust_if.hpp>
#include <boost/hana/bool.hpp>
#include <boost/hana/concept/functor.hpp>
#include <boost/hana/config.hpp>
#include <boost/hana/core/dispatch.hpp>
#include <boost/hana/if.hpp>
#include <boost/hana/transform.hpp>
namespace boost { namespace hana {
//! @cond
template <typename Xs, typename Pred, typename F>
constexpr auto adjust_if_t::operator()(Xs&& xs, Pred const& pred, F const& f) const {
using S = typename hana::tag_of<Xs>::type;
using AdjustIf = BOOST_HANA_DISPATCH_IF(adjust_if_impl<S>,
hana::Functor<S>::value
);
#ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
static_assert(hana::Functor<S>::value,
"hana::adjust_if(xs, pred, f) requires 'xs' to be a Functor");
#endif
return AdjustIf::apply(static_cast<Xs&&>(xs), pred, f);
}
//! @endcond
namespace detail {
template <typename Pred, typename F>
struct apply_if {
Pred const& pred;
F const& f;
template <typename X>
constexpr decltype(auto) helper(bool cond, X&& x) const
{ return cond ? f(static_cast<X&&>(x)) : static_cast<X&&>(x); }
template <typename X>
constexpr decltype(auto) helper(hana::true_, X&& x) const
{ return f(static_cast<X&&>(x)); }
template <typename X>
constexpr decltype(auto) helper(hana::false_, X&& x) const
{ return static_cast<X&&>(x); }
template <typename X>
constexpr decltype(auto) operator()(X&& x) const {
auto cond = hana::if_(pred(x), hana::true_c, hana::false_c);
return this->helper(cond, static_cast<X&&>(x));
}
};
}
template <typename Fun, bool condition>
struct adjust_if_impl<Fun, when<condition>> : default_ {
template <typename Xs, typename Pred, typename F>
static constexpr auto apply(Xs&& xs, Pred const& pred, F const& f) {
return hana::transform(static_cast<Xs&&>(xs),
detail::apply_if<Pred, F>{pred, f});
}
};
}} // end namespace boost::hana
#endif // !BOOST_HANA_ADJUST_IF_HPP
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