ceph/src/boost/libs/metaparse/include/boost/metaparse/v1/impl/nth_of_c_impl.hpp

   1 #ifndef BOOST_METAPARSE_V1_IMPL_NTH_OF_C_IMPL_HPP
   2 #define BOOST_METAPARSE_V1_IMPL_NTH_OF_C_IMPL_HPP
   3
   4 // Copyright Abel Sinkovics (abel@sinkovics.hu)  2013.
   5 // Distributed under the Boost Software License, Version 1.0.
   6 //    (See accompanying file LICENSE_1_0.txt or copy at
   7 //          http://www.boost.org/LICENSE_1_0.txt)
   8
   9 #include <boost/metaparse/v1/impl/skip_seq.hpp>
  10
  11 #include <boost/mpl/front.hpp>
  12 #include <boost/mpl/pop_front.hpp>
  13 #include <boost/mpl/fold.hpp>
  14
  15 namespace boost
  16 {
  17   namespace metaparse
  18   {
  19     namespace v1
  20     {
  21       namespace impl
  22       {
  23         template <int N, class Seq>
  24         struct nth_of_c_impl
  25         {
  26         private:
  27           template <class NextResult>
  28           struct apply_unchecked :
  29             nth_of_c_impl<
  30               N - 1,
  31               typename boost::mpl::pop_front<Seq>::type
  32             >::template apply<
  33               typename get_remaining<NextResult>::type,
  34               typename get_position<NextResult>::type
  35             >
  36           {};
  37         public:
  38           typedef nth_of_c_impl type;
  39
  40           template <class S, class Pos>
  41           struct apply :
  42             boost::mpl::eval_if<
  43               typename is_error<
  44                 typename boost::mpl::front<Seq>::type::template apply<S, Pos>
  45               >::type,
  46               typename boost::mpl::front<Seq>::type::template apply<S, Pos>,
  47               apply_unchecked<
  48                 typename boost::mpl::front<Seq>::type::template apply<S, Pos>
  49               >
  50             >
  51           {};
  52         };
  53
  54         template <class Seq>
  55         struct nth_of_c_impl<0, Seq>
  56         {
  57           typedef nth_of_c_impl type;
  58
  59           template <class S, class Pos>
  60           struct apply :
  61             boost::mpl::fold<
  62               typename boost::mpl::pop_front<Seq>::type,
  63               typename boost::mpl::front<Seq>::type::template apply<
  64                 S,
  65                 Pos
  66               >::type,
  67               skip_seq
  68             >
  69           {};
  70         };
  71       }
  72     }
  73   }
  74 }
  75
  76 #endif
  77