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metal/math/sqrt.hh
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25 
26 #ifndef MLN_METAL_MATH_SQRT_HH
27 # define MLN_METAL_MATH_SQRT_HH
28 
36 # include <mln/metal/bool.hh>
37 # include <mln/metal/int.hh>
38 
39 
40 # define mlc_sqrt_int(N) mln::metal::math::sqrt_int<( N )>::value
41 
42 
43 namespace mln
44 {
45 
46  namespace metal
47  {
48 
49  namespace math
50  {
51 
52  // sqrt_int<x>
53 
54  namespace impl
55  {
56 
57  template <int n, int lo = 1, int hi = n>
58  struct sqrt_int_
59  {
60  enum {
61  mid = (lo + hi + 1) / 2,
64  };
65  enum { value = n < mid * mid ? val_lo : val_hi };
66  };
67 
68  template<int n, int m>
69  struct sqrt_int_<n, m, m>
70  {
71  enum { value = m };
72  };
73 
74  // Entry.
75 
76  template <int n, bool b>
77  struct sqrt_int_if_ : sqrt_int_<n>
78  {
79  enum { value_ = sqrt_int_<n>::value,
80  reminder_ = n - value_ * value_ };
81  // FIXME: Check that reminder_ == 0.
82  };
83 
84  template <int n>
85  struct sqrt_int_if_< n, false >
86  {
87  };
88 
89  } // end of namespace mln::metal::math::impl
90 
91  template <int n>
92  struct sqrt_int : impl::sqrt_int_if_< n, (n >= 0) >
93  {
94  };
95 
96 
97  // sqrt<N>
98 
99  template <typename N>
100  struct sqrt;
101 
102  template <int n>
103  struct sqrt< int_<n> >
104  {
105  typedef int_< sqrt_int<n>::value > ret;
106  };
107 
108 
109  } // end of namespace mln::metal::math
110 
111  } // end of namespace mln::metal
112 
113 } // end of namespace mln
114 
115 
116 #endif // ! MLN_METAL_MATH_SQRT_HH