text: /*!
  @file
  Defines `boost::hana::fill`.
  
  @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_FILL_HPP
  #define BOOST_HANA_FILL_HPP
  
  #include <boost/hana/fwd/fill.hpp>
  
  #include <boost/hana/concept/functor.hpp>
  #include <boost/hana/concept/sequence.hpp>
  #include <boost/hana/config.hpp>
  #include <boost/hana/core/dispatch.hpp>
  #include <boost/hana/core/make.hpp>
  #include <boost/hana/functional/always.hpp>
  #include <boost/hana/transform.hpp>
  #include <boost/hana/unpack.hpp>
  
  
  BOOST_HANA_NAMESPACE_BEGIN
      //! @cond
      template <typename Xs, typename Value>
      constexpr auto fill_t::operator()(Xs&& xs, Value&& value) const {
          using S = typename hana::tag_of<Xs>::type;
          using Fill = BOOST_HANA_DISPATCH_IF(fill_impl<S>,
              hana::Functor<S>::value
          );
  
      #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
          static_assert(hana::Functor<S>::value,
          "hana::fill(xs, value) requires 'xs' to be a Functor");
      #endif
  
          return Fill::apply(static_cast<Xs&&>(xs),
                             static_cast<Value&&>(value));
      }
      //! @endcond
  
      template <typename Fun, bool condition>
      struct fill_impl<Fun, when<condition>> : default_ {
          template <typename Xs, typename Value>
          static constexpr auto apply(Xs&& xs, Value&& v) {
              return hana::transform(static_cast<Xs&&>(xs),
                                     hana::always(static_cast<Value&&>(v))
              );
          }
      };
  
      template <typename S>
      struct fill_impl<S, when<Sequence<S>::value>> {
          //! @cond
          template <typename V>
          struct filler {
              V const& v;
              template <typename ...Xs>
              constexpr auto operator()(Xs const& ...xs) const {
                  return hana::make<S>(((void)xs, v)...);
              }
          };
          //! @endcond
  
          template <typename Xs, typename V>
          static constexpr auto apply(Xs const& xs, V const& v) {
              return hana::unpack(xs, filler<V>{v});
          }
      };
  BOOST_HANA_NAMESPACE_END
  
  #endif // !BOOST_HANA_FILL_HPP
  