ceph/src/boost/boost/geometry/util/combine_if.hpp

   1 // Boost.Geometry (aka GGL, Generic Geometry Library)
   2
   3 // Copyright (c) 2014-2015 Samuel Debionne, Grenoble, France.
   4
   5 // This file was modified by Oracle on 2015.
   6 // Modifications copyright (c) 2015, Oracle and/or its affiliates.
   7
   8 // Contributed and/or modified by Menelaos Karavelas, on behalf of Oracle
   9
  10 // Parts of Boost.Geometry are redesigned from Geodan's Geographic Library
  11 // (geolib/GGL), copyright (c) 1995-2010 Geodan, Amsterdam, the Netherlands.
  12
  13 // Use, modification and distribution is subject to the Boost Software License,
  14 // Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
  15 // http://www.boost.org/LICENSE_1_0.txt)
  16
  17 #ifndef BOOST_GEOMETRY_UTIL_COMBINE_IF_HPP
  18 #define BOOST_GEOMETRY_UTIL_COMBINE_IF_HPP
  19
  20 #include <boost/mpl/fold.hpp>
  21 #include <boost/mpl/if.hpp>
  22 #include <boost/mpl/bind.hpp>
  23 #include <boost/mpl/set.hpp>
  24 #include <boost/mpl/insert.hpp>
  25 #include <boost/mpl/placeholders.hpp>
  26
  27
  28 namespace boost { namespace geometry
  29 {
  30
  31 namespace util
  32 {
  33
  34
  35 /*!
  36     \brief Meta-function to generate all the combination of pairs of types
  37         from a given sequence Sequence except those that does not satisfy the
  38         predicate Pred
  39     \ingroup utility
  40     \par Example
  41     \code
  42         typedef boost::mpl::vector<boost::mpl::int_<0>, boost::mpl::int_<1> > types;
  43         typedef combine_if<types, types, always<true_> >::type combinations;
  44         typedef boost::mpl::vector<
  45             pair<boost::mpl::int_<1>, boost::mpl::int_<1> >,
  46             pair<boost::mpl::int_<1>, boost::mpl::int_<0> >,
  47             pair<boost::mpl::int_<0>, boost::mpl::int_<1> >,
  48             pair<boost::mpl::int_<0>, boost::mpl::int_<0> >
  49         > result_types;
  50
  51         BOOST_MPL_ASSERT(( boost::mpl::equal<combinations, result_types> ));
  52     \endcode
  53 */
  54 template <typename Sequence1, typename Sequence2, typename Pred>
  55 struct combine_if
  56 {
  57     struct combine
  58     {
  59         template <typename Result, typename T>
  60         struct apply
  61         {
  62             typedef typename boost::mpl::fold<Sequence2, Result,
  63                 boost::mpl::if_
  64                 <
  65                     boost::mpl::bind
  66                         <
  67                             typename boost::mpl::lambda<Pred>::type,
  68                             T,
  69                             boost::mpl::_2
  70                         >,
  71                     boost::mpl::insert
  72                         <
  73                             boost::mpl::_1, boost::mpl::pair<T, boost::mpl::_2>
  74                         >,
  75                     boost::mpl::_1
  76                 >
  77             >::type type;
  78         };
  79     };
  80
  81     typedef typename boost::mpl::fold
  82         <
  83             Sequence1, boost::mpl::set0<>, combine
  84         >::type type;
  85 };
  86
  87
  88 } // namespace util
  89
  90 }} // namespace boost::geometry
  91
  92 #endif // BOOST_GEOMETRY_UTIL_COMBINE_IF_HPP