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is_a.hh
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26 
27 #ifndef MLN_METAL_IS_A_HH
28 # define MLN_METAL_IS_A_HH
29 
33 
34 # include <mln/metal/bool.hh>
35 
36 
47 # define mlc_is_a(T, M) mln::metal::is_a<T, M>
48 
49 
50 // Allows to write somthing like "mlc_is_a(T<P1,P2>, M)" without
51 // getting trouble with the preprocessor due to the 1st comma.
52 # define mlc_is_a__1comma(Tleft, Tright, M) mln::metal::is_a< Tleft,Tright , M >
53 
54 
55 
56 namespace mln
57 {
58 
59  namespace metal
60  {
61 
62  namespace internal
63  {
64 
65  typedef char yes_;
66  struct no_ { char dummy[2]; };
67 
68  template <typename T>
69  struct make_
70  {
71  static T* ptr();
72  };
73 
74  template <typename T>
75  struct make_< T& >
76  {
77  static T* ptr();
78  };
79 
80  template <typename T, template <class> class M>
81  struct helper_is_a_
82  {
83 
84  template<class V>
85  static yes_ selector(M<V>*);
86  static no_ selector(...);
87  };
88 
89  } // end of namespace mln::metal::internal
90 
91 
92 
99  template <typename T, template <class> class M>
100  struct is_a : bool_<( sizeof( internal::helper_is_a_< T, M >::selector(internal::make_< T >::ptr()) )
101  ==
102  sizeof( internal::yes_ ) )>
103  {};
104 
105  template <typename T, template <class> class M>
106  struct is_a< const T, M > : is_a< T, M >::eval
107  {};
108 
109  template <typename T, template <class> class M>
110  struct is_a< T&, M > : is_a< T, M >::eval
111  {};
112 
113  template <typename T, template <class> class M>
114  struct is_a< const T&, M > : is_a< T, M >::eval
115  {};
116 
117 
118  } // end of namespace mln::metal
119 
120 } // end of namespace mln
121 
122 
123 #endif // ! MLN_METAL_IS_A_HH