1 /*! 2 @file 3 Defines `boost::hana::remove`. 4 5 @copyright Louis Dionne 2013-2017 6 Distributed under the Boost Software License, Version 1.0. 7 (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt) 8 */ 9 10 #ifndef BOOST_HANA_REMOVE_HPP 11 #define BOOST_HANA_REMOVE_HPP 12 13 #include <boost/hana/fwd/remove.hpp> 14 15 #include <boost/hana/concept/monad_plus.hpp> 16 #include <boost/hana/config.hpp> 17 #include <boost/hana/core/dispatch.hpp> 18 #include <boost/hana/equal.hpp> 19 #include <boost/hana/filter.hpp> 20 #include <boost/hana/functional/compose.hpp> 21 #include <boost/hana/not.hpp> 22 23 24 BOOST_HANA_NAMESPACE_BEGIN 25 //! @cond 26 template <typename Xs, typename Value> operator ()(Xs && xs,Value && value) const27 constexpr auto remove_t::operator()(Xs&& xs, Value&& value) const { 28 using M = typename hana::tag_of<Xs>::type; 29 using Remove = BOOST_HANA_DISPATCH_IF(remove_impl<M>, 30 hana::MonadPlus<M>::value 31 ); 32 33 #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS 34 static_assert(hana::MonadPlus<M>::value, 35 "hana::remove(xs, value) requires 'xs' to be a MonadPlus"); 36 #endif 37 38 return Remove::apply(static_cast<Xs&&>(xs), 39 static_cast<Value&&>(value)); 40 } 41 //! @endcond 42 43 template <typename M, bool condition> 44 struct remove_impl<M, when<condition>> : default_ { 45 template <typename Xs, typename Value> applyremove_impl46 static constexpr auto apply(Xs&& xs, Value&& value) { 47 return hana::filter(static_cast<Xs&&>(xs), 48 hana::compose(hana::not_, 49 hana::equal.to(static_cast<Value&&>(value)))); 50 } 51 }; 52 BOOST_HANA_NAMESPACE_END 53 54 #endif // !BOOST_HANA_REMOVE_HPP 55