ceph/src/boost/libs/hana/include/boost/hana/take_while.hpp

   1 /*!
   2 @file
   3 Defines `boost::hana::take_while`.
   4
   5 @copyright Louis Dionne 2013-2016
   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_TAKE_WHILE_HPP
  11 #define BOOST_HANA_TAKE_WHILE_HPP
  12
  13 #include <boost/hana/fwd/take_while.hpp>
  14
  15 #include <boost/hana/concept/sequence.hpp>
  16 #include <boost/hana/config.hpp>
  17 #include <boost/hana/core/dispatch.hpp>
  18 #include <boost/hana/detail/first_unsatisfied_index.hpp>
  19 #include <boost/hana/take_front.hpp>
  20 #include <boost/hana/unpack.hpp>
  21
  22
  23 BOOST_HANA_NAMESPACE_BEGIN
  24     //! @cond
  25     template <typename Xs, typename Pred>
  26     constexpr auto take_while_t::operator()(Xs&& xs, Pred&& pred) const {
  27         using S = typename hana::tag_of<Xs>::type;
  28         using TakeWhile = BOOST_HANA_DISPATCH_IF(take_while_impl<S>,
  29             hana::Sequence<S>::value
  30         );
  31
  32     #ifndef BOOST_HANA_CONFIG_DISABLE_CONCEPT_CHECKS
  33         static_assert(hana::Sequence<S>::value,
  34         "hana::take_while(xs, pred) requires 'xs' to be a Sequence");
  35     #endif
  36
  37         return TakeWhile::apply(static_cast<Xs&&>(xs),
  38                                 static_cast<Pred&&>(pred));
  39     }
  40     //! @endcond
  41
  42     template <typename S, bool condition>
  43     struct take_while_impl<S, when<condition>> : default_ {
  44         template <typename Xs, typename Pred>
  45         static constexpr auto apply(Xs&& xs, Pred&&) {
  46             using FirstUnsatisfied = decltype(
  47                 hana::unpack(static_cast<Xs&&>(xs),
  48                              detail::first_unsatisfied_index<Pred&&>{})
  49             );
  50             return hana::take_front(static_cast<Xs&&>(xs), FirstUnsatisfied{});
  51         }
  52     };
  53 BOOST_HANA_NAMESPACE_END
  54
  55 #endif // !BOOST_HANA_TAKE_WHILE_HPP