/*! @file Defines `boost::hana::extend`. @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_EXTEND_HPP #define BOOST_HANA_EXTEND_HPP #include <boost/hana/fwd/extend.hpp> #include <boost/hana/concept/comonad.hpp> #include <boost/hana/config.hpp> #include <boost/hana/core/dispatch.hpp> #include <boost/hana/duplicate.hpp> #include <boost/hana/transform.hpp> BOOST_HANA_NAMESPACE_BEGIN //! @cond template <typename W_, typename F> constexpr decltype(auto) extend_t::operator()(W_&& w, F&& f) const { using W = typename hana::tag_of<W_>::type; using Extend = BOOST_HANA_DISPATCH_IF(extend_impl<W>, hana::Comonad<W>::value ); #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS static_assert(hana::Comonad<W>::value, "hana::extend(w, f) requires 'w' to be a Comonad"); #endif return Extend::apply(static_cast<W_&&>(w), static_cast<F&&>(f)); } //! @endcond template <typename W, bool condition> struct extend_impl<W, when<condition>> : default_ { template <typename X, typename F> static constexpr decltype(auto) apply(X&& x, F&& f) { return hana::transform(hana::duplicate(static_cast<X&&>(x)), static_cast<F&&>(f)); } }; BOOST_HANA_NAMESPACE_END #endif // !BOOST_HANA_EXTEND_HPP