1 //  Copyright John Maddock 2007.
2 
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 <boost/mpl/has_xxx.hpp>
29 #include <boost/type_traits/integral_constant.hpp>
30 
31 namespace boost{ namespace math{ namespace tools{
32 
33 namespace detail{
34 
35 BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF(has_value_type, value_type, true)
36 BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF(has_policy_type, policy_type, true)
37 BOOST_MPL_HAS_XXX_TRAIT_NAMED_DEF(has_backend_type, backend_type, true)
38 
39 template<class D>
40 char cdf(const D& ...);
41 template<class D>
42 char quantile(const D& ...);
43 
44 template <class D>
45 struct has_cdf
46 {
47    static D d;
48    BOOST_STATIC_CONSTANT(bool, value = sizeof(cdf(d, 0.0f)) != 1);
49 };
50 
51 template <class D>
52 struct has_quantile
53 {
54    static D d;
55    BOOST_STATIC_CONSTANT(bool, value = sizeof(quantile(d, 0.0f)) != 1);
56 };
57 
58 template <class D>
59 struct is_distribution_imp
60 {
61    BOOST_STATIC_CONSTANT(bool, value =
62       has_quantile<D>::value
63       && has_cdf<D>::value
64       && has_value_type<D>::value
65       && has_policy_type<D>::value);
66 };
67 
68 template <class sig, sig val>
69 struct result_tag{};
70 
71 template <class D>
72 double test_has_location(const volatile result_tag<typename D::value_type (D::*)()const, &D::location>*);
73 template <class D>
74 char test_has_location(...);
75 
76 template <class D>
77 double test_has_scale(const volatile result_tag<typename D::value_type (D::*)()const, &D::scale>*);
78 template <class D>
79 char test_has_scale(...);
80 
81 template <class D, bool b>
82 struct is_scaled_distribution_helper
83 {
84    BOOST_STATIC_CONSTANT(bool, value = false);
85 };
86 
87 template <class D>
88 struct is_scaled_distribution_helper<D, true>
89 {
90    BOOST_STATIC_CONSTANT(bool, value =
91       (sizeof(test_has_location<D>(0)) != 1)
92       &&
93       (sizeof(test_has_scale<D>(0)) != 1));
94 };
95 
96 template <class D>
97 struct is_scaled_distribution_imp
98 {
99    BOOST_STATIC_CONSTANT(bool, value = (::boost::math::tools::detail::is_scaled_distribution_helper<D, ::boost::math::tools::detail::is_distribution_imp<D>::value>::value));
100 };
101 
102 } // namespace detail
103 
104 template <class T> struct is_distribution : public boost::integral_constant<bool, ::boost::math::tools::detail::is_distribution_imp<T>::value> {};
105 template <class T> struct is_scaled_distribution : public boost::integral_constant<bool, ::boost::math::tools::detail::is_scaled_distribution_imp<T>::value> {};
106 
107 }}}
108 
109 #endif
110 
111 
112