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converts_to.hh
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26 
27 #ifndef MLN_METAL_CONVERTS_TO_HH
28 # define MLN_METAL_CONVERTS_TO_HH
29 
34 
35 # include <mln/metal/is_a.hh>
36 # include <mln/metal/const.hh>
37 # include <mln/core/def/coord.hh>
38 
39 
40 # define mlc_converts_to(T, U) mln::metal::converts_to< T, U >
41 
42 
43 
44 namespace mln
45 {
46 
47  // Forward declarations.
48  namespace value {
49  template <unsigned n> struct int_u;
50  template <unsigned n> struct int_s;
51  }
52 
53 
54  namespace metal
55  {
56 
57  namespace internal
58  {
59 
60  struct eat // Required by g++-2.95 for selector to work.
61  {
62  template <typename T> eat(const volatile T&);
63  template <typename T> eat(T&);
64  };
65 
66  template <typename T, typename U>
67  struct helper_converts_to_
68  {
69  static yes_ selector(U, int);
70  static no_ selector(eat, ...);
71  };
72 
73  } // end of namespace mln::metal::internal
74 
75 
76 
81  template <typename T, typename U>
82  struct converts_to : bool_<( sizeof(internal::helper_converts_to_<T, U>
83  ::selector(*internal::make_<mlc_const(T)>::ptr(),
84  0) )
85  ==
86  sizeof(internal::yes_) )>
87  {};
88 
89 
90  template <typename T, typename U>
91  struct converts_to<T*, U*> : converts_to<T, U>
92  {};
93 
94  template <typename T, typename U>
95  struct converts_to<T**, U**> : false_
96  {};
97 
98 
99 
100  // Below, a few hacks to quiet g++-3.4 warnings:
101 
102  template <> struct converts_to< float, int > : true_ {};
103  template <> struct converts_to< float, def::coord > : true_ {};
104  template <unsigned n> struct converts_to< float, value::int_u<n> > : true_ {};
105  template <unsigned n> struct converts_to< float, value::int_s<n> > : true_ {};
106 
107  template <> struct converts_to< double, int > : true_ {};
108  template <> struct converts_to< double, def::coord > : true_ {};
109  template <unsigned n> struct converts_to< double, value::int_u<n> > : true_ {};
110  template <unsigned n> struct converts_to< double, value::int_s<n> > : true_ {};
111 
112  // End of hacks.
113 
114  } // end of namespace mln::metal
115 
116 
117 
118 } // end of namespace mln
119 
120 
121 #endif // ! MLN_METAL_CONVERTS_TO_HH