1 |
|
---|
2 | #include <boost/mpl/map.hpp>
|
---|
3 | #include <boost/mpl/pair.hpp>
|
---|
4 | #include <boost/mpl/erase_key.hpp>
|
---|
5 | #include <boost/mpl/for_each.hpp>
|
---|
6 | #include <boost/mpl/insert.hpp>
|
---|
7 | #include <boost/mpl/begin_end.hpp>
|
---|
8 | #include <boost/mpl/less.hpp>
|
---|
9 | #include <boost/mpl/size.hpp>
|
---|
10 | #include <boost/mpl/deref.hpp>
|
---|
11 | #include <iostream>
|
---|
12 |
|
---|
13 |
|
---|
14 | namespace mpl = boost::mpl;
|
---|
15 |
|
---|
16 | //=============================================================================
|
---|
17 | //Template meta function that joins two maps (normally in a header file)
|
---|
18 | template< class, class MapL, class MapR >
|
---|
19 | struct join_maps_imp;
|
---|
20 |
|
---|
21 | //=============================================================================
|
---|
22 | template< class MapL, class MapR >
|
---|
23 | struct join_maps
|
---|
24 | {
|
---|
25 | typedef typename join_maps_imp< typename mpl::less< typename mpl::size<MapL>::type
|
---|
26 | , typename mpl::size<MapR>::type >::type
|
---|
27 | , MapL
|
---|
28 | , MapR
|
---|
29 | >::type type;
|
---|
30 | };
|
---|
31 |
|
---|
32 | //=============================================================================
|
---|
33 | //MapR is smaller than MapL, so add R to L
|
---|
34 | template< class MapL, class MapR >
|
---|
35 | struct join_maps_imp<mpl::false_, MapL, MapR>
|
---|
36 | {
|
---|
37 | typedef typename join_maps_imp<mpl::true_, MapR, MapL>::type type;
|
---|
38 | };
|
---|
39 |
|
---|
40 |
|
---|
41 | //=============================================================================
|
---|
42 | namespace join_maps_detail
|
---|
43 | {
|
---|
44 | //The loop
|
---|
45 | template<bool done, class iter, class end_iter, class OldMap>
|
---|
46 | struct next_elem
|
---|
47 | {
|
---|
48 | typedef typename mpl::deref< iter >::type MapElem;
|
---|
49 | typedef typename mpl::insert< OldMap, MapElem >::type NewMap;
|
---|
50 | typedef typename mpl::next<iter>::type next_iter;
|
---|
51 | typedef typename next_elem<boost::is_same<next_iter, end_iter>::value
|
---|
52 | , next_iter
|
---|
53 | , end_iter
|
---|
54 | , NewMap >::type type;
|
---|
55 | };
|
---|
56 |
|
---|
57 | //Loop termination
|
---|
58 | template<class iter, class end_iter, class NewMap>
|
---|
59 | struct next_elem<true, iter, end_iter, NewMap >
|
---|
60 | {
|
---|
61 | typedef NewMap type;
|
---|
62 | };
|
---|
63 |
|
---|
64 | };
|
---|
65 |
|
---|
66 | //=============================================================================
|
---|
67 | //MapL is smaller than MapR, so add L to R
|
---|
68 | template< class MapL, class MapR >
|
---|
69 | struct join_maps_imp<mpl::true_, MapL, MapR>
|
---|
70 | {
|
---|
71 |
|
---|
72 | //Initialize the loop
|
---|
73 | typedef typename mpl::begin<MapL>::type iter;
|
---|
74 | typedef typename mpl::end<MapL>::type end_iter;
|
---|
75 |
|
---|
76 | typedef typename join_maps_detail::next_elem<false
|
---|
77 | , iter
|
---|
78 | , end_iter
|
---|
79 | , MapR>::type type;
|
---|
80 |
|
---|
81 | };
|
---|
82 |
|
---|
83 | //=============================================================================
|
---|
84 | template<int i>
|
---|
85 | struct print {};
|
---|
86 |
|
---|
87 | //=============================================================================
|
---|
88 | template<int i>
|
---|
89 | std::ostream& operator<<(std::ostream& out, const print<i>&)
|
---|
90 | {
|
---|
91 | out << i;
|
---|
92 | return out;
|
---|
93 | }
|
---|
94 |
|
---|
95 | //=============================================================================
|
---|
96 | struct map_printer
|
---|
97 | {
|
---|
98 | template <class T>
|
---|
99 | inline void operator() (T) const
|
---|
100 | {
|
---|
101 | std::cout << " " << typename T::second();
|
---|
102 | }
|
---|
103 | };
|
---|
104 |
|
---|
105 | /*###################################################################*/
|
---|
106 | int main(int argc, const char* argv[])
|
---|
107 | {
|
---|
108 | //Create a couple of maps using insert (this replicates the actual code)
|
---|
109 | typedef mpl::insert<mpl::map<>, mpl::pair< mpl::int_<0>, print<0> > >::type map0;
|
---|
110 | typedef mpl::insert<map0 , mpl::pair< mpl::int_<1>, print<1> > >::type map1;
|
---|
111 | typedef mpl::insert<map1 , mpl::pair< mpl::int_<2>, print<2> > >::type map2;
|
---|
112 |
|
---|
113 | typedef mpl::insert<mpl::map<>, mpl::pair< mpl::int_<3>, print<3> > >::type map3;
|
---|
114 | typedef mpl::insert<map3 , mpl::pair< mpl::int_<4>, print<4> > >::type map4;
|
---|
115 | typedef mpl::insert<map4 , mpl::pair< mpl::int_<5>, print<5> > >::type map5;
|
---|
116 |
|
---|
117 | //Erease a couple of keys
|
---|
118 | typedef mpl::erase_key<map2, mpl::int_<1> >::type map_erase1;
|
---|
119 | typedef mpl::erase_key<map5, mpl::int_<4> >::type map_erase2;
|
---|
120 |
|
---|
121 | //Join the maps into a single map
|
---|
122 | typedef join_maps< map2 , map_erase2 >::type join1;
|
---|
123 | typedef join_maps< map_erase1, map5 >::type join2;
|
---|
124 | typedef join_maps< map_erase1, map_erase2 >::type join3;
|
---|
125 |
|
---|
126 | //Print out the resuling maps
|
---|
127 | std::cout << std::endl;
|
---|
128 | boost::mpl::for_each< join1 >(map_printer()); //Works
|
---|
129 |
|
---|
130 | std::cout << std::endl;
|
---|
131 | boost::mpl::for_each< join2 >(map_printer()); //Works
|
---|
132 |
|
---|
133 | std::cout << std::endl;
|
---|
134 | boost::mpl::for_each< join3 >(map_printer()); //MSVC 9 error (works with CYGWIN GCC 4.3.2 )
|
---|
135 |
|
---|
136 | std::cout << std::endl;
|
---|
137 |
|
---|
138 | }
|
---|
139 |
|
---|