boost/hana/replace.hpp

   1 /*!
   2 @file
   3 Defines `boost::hana::replace`.
   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_REPLACE_HPP
  11 #define BOOST_HANA_REPLACE_HPP
  12
  13 #include <boost/hana/fwd/replace.hpp>
  14
  15 #include <boost/hana/concept/functor.hpp>
  16 #include <boost/hana/config.hpp>
  17 #include <boost/hana/core/dispatch.hpp>
  18 #include <boost/hana/equal.hpp>
  19 #include <boost/hana/replace_if.hpp>
  20
  21
  22 BOOST_HANA_NAMESPACE_BEGIN
  23     //! @cond
  24     template <typename Xs, typename OldVal, typename NewVal>
  25     constexpr auto replace_t::operator()(Xs&& xs, OldVal&& oldval, NewVal&& newval) const {
  26         using S = typename hana::tag_of<Xs>::type;
  27         using Replace = BOOST_HANA_DISPATCH_IF(replace_impl<S>,
  28             hana::Functor<S>::value
  29         );
  30
  31     #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
  32         static_assert(hana::Functor<S>::value,
  33         "hana::replace(xs, oldval, newval) requires 'xs' to be a Functor");
  34     #endif
  35
  36         return Replace::apply(static_cast<Xs&&>(xs),
  37                               static_cast<OldVal&&>(oldval),
  38                               static_cast<NewVal&&>(newval));
  39     }
  40     //! @endcond
  41
  42     template <typename Fun, bool condition>
  43     struct replace_impl<Fun, when<condition>> : default_ {
  44         template <typename Xs, typename OldVal, typename NewVal>
  45         static constexpr decltype(auto)
  46         apply(Xs&& xs, OldVal&& oldval, NewVal&& newval) {
  47             return hana::replace_if(
  48                 static_cast<Xs&&>(xs),
  49                 hana::equal.to(static_cast<OldVal&&>(oldval)),
  50                 static_cast<NewVal&&>(newval)
  51             );
  52         }
  53     };
  54 BOOST_HANA_NAMESPACE_END
  55
  56 #endif // !BOOST_HANA_REPLACE_HPP