85 lines
2.5 KiB
Plaintext
85 lines
2.5 KiB
Plaintext
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// (C) Copyright John Maddock 2006.
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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_POWM1
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#define BOOST_MATH_POWM1
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#ifdef _MSC_VER
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#pragma once
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#pragma warning(push)
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#pragma warning(disable:4702) // Unreachable code (release mode only warning)
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#endif
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#include <boost/math/special_functions/math_fwd.hpp>
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#include <boost/math/special_functions/log1p.hpp>
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#include <boost/math/special_functions/expm1.hpp>
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#include <boost/math/special_functions/trunc.hpp>
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#include <boost/assert.hpp>
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namespace boost{ namespace math{ namespace detail{
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template <class T, class Policy>
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inline T powm1_imp(const T x, const T y, const Policy& pol)
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{
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BOOST_MATH_STD_USING
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static const char* function = "boost::math::powm1<%1%>(%1%, %1%)";
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if (x > 0)
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{
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if ((fabs(y * (x - 1)) < 0.5) || (fabs(y) < 0.2))
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{
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// We don't have any good/quick approximation for log(x) * y
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// so just try it and see:
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T l = y * log(x);
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if (l < 0.5)
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return boost::math::expm1(l);
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if (l > boost::math::tools::log_max_value<T>())
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return boost::math::policies::raise_overflow_error<T>(function, 0, pol);
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// fall through....
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}
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}
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else
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{
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// y had better be an integer:
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if (boost::math::trunc(y) != y)
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return boost::math::policies::raise_domain_error<T>(function, "For non-integral exponent, expected base > 0 but got %1%", x, pol);
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if (boost::math::trunc(y / 2) == y / 2)
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return powm1_imp(T(-x), y, pol);
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}
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return pow(x, y) - 1;
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}
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} // detail
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template <class T1, class T2>
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inline typename tools::promote_args<T1, T2>::type
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powm1(const T1 a, const T2 z)
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{
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typedef typename tools::promote_args<T1, T2>::type result_type;
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return detail::powm1_imp(static_cast<result_type>(a), static_cast<result_type>(z), policies::policy<>());
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}
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template <class T1, class T2, class Policy>
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inline typename tools::promote_args<T1, T2>::type
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powm1(const T1 a, const T2 z, const Policy& pol)
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{
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typedef typename tools::promote_args<T1, T2>::type result_type;
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return detail::powm1_imp(static_cast<result_type>(a), static_cast<result_type>(z), pol);
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}
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} // namespace math
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} // namespace boost
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#ifdef _MSC_VER
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#pragma warning(pop)
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#endif
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#endif // BOOST_MATH_POWM1
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