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1 // (C) Copyright John Maddock 2006.
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2 // Use, modification and distribution are subject to the
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3 // Boost Software License, Version 1.0. (See accompanying file
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4 // LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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5
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6 #ifndef BOOST_MATH_POWM1
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7 #define BOOST_MATH_POWM1
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8
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9 #ifdef _MSC_VER
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10 #pragma once
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11 #endif
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12
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13 #include <boost/math/special_functions/math_fwd.hpp>
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14 #include <boost/math/special_functions/log1p.hpp>
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15 #include <boost/math/special_functions/expm1.hpp>
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16 #include <boost/assert.hpp>
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17
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18 namespace boost{ namespace math{ namespace detail{
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19
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20 template <class T, class Policy>
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21 inline T powm1_imp(const T a, const T z, const Policy& pol)
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22 {
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23 BOOST_MATH_STD_USING
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24
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25 if((fabs(a) < 1) || (fabs(z) < 1))
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26 {
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27 T p = log(a) * z;
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28 if(fabs(p) < 2)
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29 return boost::math::expm1(p, pol);
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30 // otherwise fall though:
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31 }
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32 return pow(a, z) - 1;
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33 }
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34
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35 } // detail
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36
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37 template <class T1, class T2>
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38 inline typename tools::promote_args<T1, T2>::type
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39 powm1(const T1 a, const T2 z)
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40 {
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41 typedef typename tools::promote_args<T1, T2>::type result_type;
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42 return detail::powm1_imp(static_cast<result_type>(a), static_cast<result_type>(z), policies::policy<>());
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43 }
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44
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45 template <class T1, class T2, class Policy>
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46 inline typename tools::promote_args<T1, T2>::type
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47 powm1(const T1 a, const T2 z, const Policy& pol)
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48 {
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49 typedef typename tools::promote_args<T1, T2>::type result_type;
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50 return detail::powm1_imp(static_cast<result_type>(a), static_cast<result_type>(z), pol);
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51 }
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52
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53 } // namespace math
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54 } // namespace boost
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55
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56 #endif // BOOST_MATH_POWM1
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57
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58
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59
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60
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61
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