72 lines
2.0 KiB
C++
72 lines
2.0 KiB
C++
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// (C) Copyright John Maddock 2015.
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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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#ifndef BOOST_MATH_SPECIAL_ULP_HPP
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#define BOOST_MATH_SPECIAL_ULP_HPP
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#ifdef _MSC_VER
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#pragma once
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#endif
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#include <boost/math/special_functions/math_fwd.hpp>
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#include <boost/math/policies/error_handling.hpp>
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#include <boost/math/special_functions/fpclassify.hpp>
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#include <boost/math/special_functions/next.hpp>
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namespace boost{ namespace math{ namespace detail{
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template <class T, class Policy>
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T ulp_imp(const T& val, const Policy& pol)
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{
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BOOST_MATH_STD_USING
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int expon;
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static const char* function = "ulp<%1%>(%1%)";
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int fpclass = (boost::math::fpclassify)(val);
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if(fpclass == (int)FP_NAN)
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{
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return policies::raise_domain_error<T>(
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function,
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"Argument must be finite, but got %1%", val, pol);
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}
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else if((fpclass == (int)FP_INFINITE) || (fabs(val) >= tools::max_value<T>()))
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{
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return (val < 0 ? -1 : 1) * policies::raise_overflow_error<T>(function, 0, pol);
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}
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else if(fpclass == FP_ZERO)
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return detail::get_smallest_value<T>();
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//
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// This code is almost the same as that for float_next, except for negative integers,
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// where we preserve the relation ulp(x) == ulp(-x) as does Java:
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//
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frexp(fabs(val), &expon);
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T diff = ldexp(T(1), expon - tools::digits<T>());
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if(diff == 0)
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diff = detail::get_smallest_value<T>();
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return diff;
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}
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}
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template <class T, class Policy>
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inline typename tools::promote_args<T>::type ulp(const T& val, const Policy& pol)
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{
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typedef typename tools::promote_args<T>::type result_type;
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return detail::ulp_imp(static_cast<result_type>(val), pol);
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}
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template <class T>
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inline typename tools::promote_args<T>::type ulp(const T& val)
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{
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return ulp(val, policies::policy<>());
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}
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}} // namespaces
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#endif // BOOST_MATH_SPECIAL_ULP_HPP
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