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
93