ceph/src/boost/boost/math/tools/traits.hpp

   1 //  Copyright John Maddock 2007.
   2 //  Copyright Matt Borland 2021.
   3 //  Use, modification and distribution are subject to the
   4 //  Boost Software License, Version 1.0. (See accompanying file
   5 //  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   6
   7 /*
   8 This header defines two traits classes, both in namespace boost::math::tools.
   9
  10 is_distribution<D>::value is true iff D has overloaded "cdf" and
  11 "quantile" functions, plus member typedefs value_type and policy_type.
  12 It's not much of a definitive test frankly,
  13 but if it looks like a distribution and quacks like a distribution
  14 then it must be a distribution.
  15
  16 is_scaled_distribution<D>::value is true iff D is a distribution
  17 as defined above, and has member functions "scale" and "location".
  18
  19 */
  20
  21 #ifndef BOOST_STATS_IS_DISTRIBUTION_HPP
  22 #define BOOST_STATS_IS_DISTRIBUTION_HPP
  23
  24 #ifdef _MSC_VER
  25 #pragma once
  26 #endif
  27
  28 #include <type_traits>
  29
  30 namespace boost{ namespace math{ namespace tools{
  31
  32 namespace detail{
  33
  34 #define BOOST_MATH_HAS_NAMED_TRAIT(trait, name)                         \
  35 template <typename T>                                                   \
  36 class trait                                                             \
  37 {                                                                       \
  38 private:                                                                \
  39    using yes = char;                                                    \
  40    struct no { char x[2]; };                                            \
  41                                                                         \
  42    template <typename U>                                                \
  43    static yes test(typename U::name* = nullptr);                        \
  44                                                                         \
  45    template <typename U>                                                \
  46    static no test(...);                                                 \
  47                                                                         \
  48 public:                                                                 \
  49    static constexpr bool value = (sizeof(test<T>(0)) == sizeof(char));  \
  50 };
  51
  52 BOOST_MATH_HAS_NAMED_TRAIT(has_value_type, value_type)
  53 BOOST_MATH_HAS_NAMED_TRAIT(has_policy_type, policy_type)
  54 BOOST_MATH_HAS_NAMED_TRAIT(has_backend_type, backend_type)
  55
  56 template <typename D>
  57 char cdf(const D& ...);
  58 template <typename D>
  59 char quantile(const D& ...);
  60
  61 template <typename D>
  62 struct has_cdf
  63 {
  64    static D d;
  65    static constexpr bool value = sizeof(cdf(d, 0.0f)) != 1;
  66 };
  67
  68 template <typename D>
  69 struct has_quantile
  70 {
  71    static D d;
  72    static constexpr bool value = sizeof(quantile(d, 0.0f)) != 1;
  73 };
  74
  75 template <typename D>
  76 struct is_distribution_imp
  77 {
  78    static constexpr bool value =
  79       has_quantile<D>::value
  80       && has_cdf<D>::value
  81       && has_value_type<D>::value
  82       && has_policy_type<D>::value;
  83 };
  84
  85 template <typename sig, sig val>
  86 struct result_tag{};
  87
  88 template <typename D>
  89 double test_has_location(const volatile result_tag<typename D::value_type (D::*)()const, &D::location>*);
  90 template <typename D>
  91 char test_has_location(...);
  92
  93 template <typename D>
  94 double test_has_scale(const volatile result_tag<typename D::value_type (D::*)()const, &D::scale>*);
  95 template <typename D>
  96 char test_has_scale(...);
  97
  98 template <typename D, bool b>
  99 struct is_scaled_distribution_helper
 100 {
 101    static constexpr bool value = false;
 102 };
 103
 104 template <typename D>
 105 struct is_scaled_distribution_helper<D, true>
 106 {
 107    static constexpr bool value =
 108       (sizeof(test_has_location<D>(0)) != 1)
 109       &&
 110       (sizeof(test_has_scale<D>(0)) != 1);
 111 };
 112
 113 template <typename D>
 114 struct is_scaled_distribution_imp
 115 {
 116    static constexpr bool value = (::boost::math::tools::detail::is_scaled_distribution_helper<D, ::boost::math::tools::detail::is_distribution_imp<D>::value>::value);
 117 };
 118
 119 } // namespace detail
 120
 121 template <typename T> struct is_distribution : public std::integral_constant<bool, ::boost::math::tools::detail::is_distribution_imp<T>::value> {};
 122 template <typename T> struct is_scaled_distribution : public std::integral_constant<bool, ::boost::math::tools::detail::is_scaled_distribution_imp<T>::value> {};
 123
 124 }}}
 125
 126 #endif
 127
 128