585da50d7d
This PR adds the code of Boost.Math as of version 1.89 into the third-party directory, as discussed in a recent RFC [1]. The goal is for this code to be used as a back-end for the C++17 Math Special Functions. As explained in third-paty/README.md, this code is cleared for usage inside libc++ for the Math Special functions, however the LLVM Foundation should be consulted before using this code anywhere else in the LLVM project, due to the fact that it is under the Boost Software License (as opposed to the usual LLVM license). See the RFC [1] for more details. [1]: https://discourse.llvm.org/t/rfc-libc-taking-a-dependency-on-boost-math-for-the-c-17-math-special-functions
141 lines
4.5 KiB
C++
141 lines
4.5 KiB
C++
// Copyright John Maddock 2007.
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// Copyright Matt Borland 2021.
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// Use, modification and distribution are subject to the
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// Boost Software License, Version 1.0. (See accompanying file
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// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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/*
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This header defines two traits classes, both in namespace boost::math::tools.
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is_distribution<D>::value is true iff D has overloaded "cdf" and
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"quantile" functions, plus member typedefs value_type and policy_type.
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It's not much of a definitive test frankly,
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but if it looks like a distribution and quacks like a distribution
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then it must be a distribution.
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is_scaled_distribution<D>::value is true iff D is a distribution
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as defined above, and has member functions "scale" and "location".
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*/
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#ifndef BOOST_STATS_IS_DISTRIBUTION_HPP
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#define BOOST_STATS_IS_DISTRIBUTION_HPP
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#ifdef _MSC_VER
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#pragma once
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#endif
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#include <type_traits>
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namespace boost{ namespace math{ namespace tools{
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namespace detail{
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#define BOOST_MATH_HAS_NAMED_TRAIT(trait, name) \
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template <typename T> \
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class trait \
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{ \
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private: \
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using yes = char; \
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struct no { char x[2]; }; \
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\
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template <typename U> \
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static yes test(typename U::name* = nullptr); \
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\
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template <typename U> \
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static no test(...); \
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\
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public: \
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static constexpr bool value = (sizeof(test<T>(0)) == sizeof(char)); \
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};
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BOOST_MATH_HAS_NAMED_TRAIT(has_value_type, value_type)
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BOOST_MATH_HAS_NAMED_TRAIT(has_policy_type, policy_type)
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BOOST_MATH_HAS_NAMED_TRAIT(has_backend_type, backend_type)
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// C++17-esque helpers
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#if defined(__cpp_variable_templates) && __cpp_variable_templates >= 201304L
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template <typename T>
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constexpr bool has_value_type_v = has_value_type<T>::value;
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template <typename T>
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constexpr bool has_policy_type_v = has_policy_type<T>::value;
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template <typename T>
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constexpr bool has_backend_type_v = has_backend_type<T>::value;
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#endif
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template <typename D>
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char cdf(const D&, ...);
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template <typename D>
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char quantile(const D&, ...);
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template <typename D>
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struct has_cdf
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{
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static D d;
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static constexpr bool value = sizeof(cdf(d, 0.0f)) != 1;
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};
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template <typename D>
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struct has_quantile
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{
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static D d;
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static constexpr bool value = sizeof(quantile(d, 0.0f)) != 1;
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};
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template <typename D>
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struct is_distribution_imp
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{
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static constexpr bool value =
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has_quantile<D>::value
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&& has_cdf<D>::value
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&& has_value_type<D>::value
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&& has_policy_type<D>::value;
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};
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template <typename sig, sig val>
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struct result_tag{};
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template <typename D>
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double test_has_location(const volatile result_tag<typename D::value_type (D::*)()const, &D::location>*);
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template <typename D>
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char test_has_location(...);
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template <typename D>
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double test_has_scale(const volatile result_tag<typename D::value_type (D::*)()const, &D::scale>*);
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template <typename D>
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char test_has_scale(...);
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template <typename D, bool b>
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struct is_scaled_distribution_helper
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{
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static constexpr bool value = false;
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};
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template <typename D>
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struct is_scaled_distribution_helper<D, true>
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{
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static constexpr bool value =
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(sizeof(test_has_location<D>(0)) != 1)
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&&
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(sizeof(test_has_scale<D>(0)) != 1);
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};
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template <typename D>
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struct is_scaled_distribution_imp
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{
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static constexpr bool value = (::boost::math::tools::detail::is_scaled_distribution_helper<D, ::boost::math::tools::detail::is_distribution_imp<D>::value>::value);
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};
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} // namespace detail
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template <typename T> struct is_distribution : public std::integral_constant<bool, ::boost::math::tools::detail::is_distribution_imp<T>::value> {};
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template <typename T> struct is_scaled_distribution : public std::integral_constant<bool, ::boost::math::tools::detail::is_scaled_distribution_imp<T>::value> {};
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}}}
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#endif
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