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if.hh
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25 
26 #ifndef MLN_METAL_IF_HH
27 # define MLN_METAL_IF_HH
28 
34 # include <mln/metal/bool.hh>
35 
36 # define mlc_if(Cond, Then, Else) typename mln::metal::if_< Cond, Then, Else >::ret
37 
38 
39 
40 namespace mln
41 {
42 
43  namespace metal
44  {
45 
46  namespace internal
47  {
48 
49  template <bool cond, typename Then, typename Else>
50  struct helper_if_;
51 
52  template <typename Then, typename Else>
53  struct helper_if_< true, Then, Else >
54  {
55  typedef Then ret;
56  };
57 
58  template <typename Then, typename Else>
59  struct helper_if_< false, Then, Else >
60  {
61  typedef Else ret;
62  };
63 
64  } // end of namespace mln::metal::internal
65 
66 
71  template <typename Cond, typename Then, typename Else>
72  struct if_ : internal::helper_if_< Cond::value, Then, Else >
73  {
74  // ret is inherited.
75  };
76 
77 
78  } // end of namespace mln::metal
79 
80 } // end of namespace mln
81 
82 
83 #endif // ! MLN_METAL_IF_HH