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      1 // This file is part of Eigen, a lightweight C++ template library
      2 // for linear algebra.
      3 //
      4 // Copyright (C) 2010 Jitse Niesen <jitse (at) maths.leeds.ac.uk>
      5 //
      6 // This Source Code Form is subject to the terms of the Mozilla
      7 // Public License v. 2.0. If a copy of the MPL was not distributed
      8 // with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
      9 
     10 #ifndef EIGEN_STEM_FUNCTION
     11 #define EIGEN_STEM_FUNCTION
     12 
     13 namespace Eigen {
     14 
     15 /** \ingroup MatrixFunctions_Module
     16   * \brief Stem functions corresponding to standard mathematical functions.
     17   */
     18 template <typename Scalar>
     19 class StdStemFunctions
     20 {
     21   public:
     22 
     23     /** \brief The exponential function (and its derivatives). */
     24     static Scalar exp(Scalar x, int)
     25     {
     26       return std::exp(x);
     27     }
     28 
     29     /** \brief Cosine (and its derivatives). */
     30     static Scalar cos(Scalar x, int n)
     31     {
     32       Scalar res;
     33       switch (n % 4) {
     34       case 0:
     35 	res = std::cos(x);
     36 	break;
     37       case 1:
     38 	res = -std::sin(x);
     39 	break;
     40       case 2:
     41 	res = -std::cos(x);
     42 	break;
     43       case 3:
     44 	res = std::sin(x);
     45 	break;
     46       }
     47       return res;
     48     }
     49 
     50     /** \brief Sine (and its derivatives). */
     51     static Scalar sin(Scalar x, int n)
     52     {
     53       Scalar res;
     54       switch (n % 4) {
     55       case 0:
     56 	res = std::sin(x);
     57 	break;
     58       case 1:
     59 	res = std::cos(x);
     60 	break;
     61       case 2:
     62 	res = -std::sin(x);
     63 	break;
     64       case 3:
     65 	res = -std::cos(x);
     66 	break;
     67       }
     68       return res;
     69     }
     70 
     71     /** \brief Hyperbolic cosine (and its derivatives). */
     72     static Scalar cosh(Scalar x, int n)
     73     {
     74       Scalar res;
     75       switch (n % 2) {
     76       case 0:
     77 	res = std::cosh(x);
     78 	break;
     79       case 1:
     80 	res = std::sinh(x);
     81 	break;
     82       }
     83       return res;
     84     }
     85 
     86     /** \brief Hyperbolic sine (and its derivatives). */
     87     static Scalar sinh(Scalar x, int n)
     88     {
     89       Scalar res;
     90       switch (n % 2) {
     91       case 0:
     92 	res = std::sinh(x);
     93 	break;
     94       case 1:
     95 	res = std::cosh(x);
     96 	break;
     97       }
     98       return res;
     99     }
    100 
    101 }; // end of class StdStemFunctions
    102 
    103 } // end namespace Eigen
    104 
    105 #endif // EIGEN_STEM_FUNCTION
    106