/*! @file Defines `boost::hana::adjust_if`. @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_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> BOOST_HANA_NAMESPACE_BEGIN //! @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}); } }; BOOST_HANA_NAMESPACE_END #endif // !BOOST_HANA_ADJUST_IF_HPP