xref: /external/eigen/unsupported/Eigen/src/MatrixFunctions/StemFunction.h

// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2010 Jitse Niesen <jitse@maths.leeds.ac.uk>
//
// This Source Code Form is subject to the terms of the Mozilla
// Public License v. 2.0. If a copy of the MPL was not distributed
// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.

#ifndef EIGEN_STEM_FUNCTION
#define EIGEN_STEM_FUNCTION

namespace Eigen {

/** \ingroup MatrixFunctions_Module
  * \brief Stem functions corresponding to standard mathematical functions.
  */
template <typename Scalar>
class StdStemFunctions
{
  public:

    /** \brief The exponential function (and its derivatives). */
    static Scalar exp(Scalar x, int)
    {
      return std::exp(x);
    }

    /** \brief Cosine (and its derivatives). */
    static Scalar cos(Scalar x, int n)
    {
      Scalar res;
      switch (n % 4) {
      case 0:
	res = std::cos(x);
	break;
      case 1:
	res = -std::sin(x);
	break;
      case 2:
	res = -std::cos(x);
	break;
      case 3:
	res = std::sin(x);
	break;
      }
      return res;
    }

    /** \brief Sine (and its derivatives). */
    static Scalar sin(Scalar x, int n)
    {
      Scalar res;
      switch (n % 4) {
      case 0:
	res = std::sin(x);
	break;
      case 1:
	res = std::cos(x);
	break;
      case 2:
	res = -std::sin(x);
	break;
      case 3:
	res = -std::cos(x);
	break;
      }
      return res;
    }

    /** \brief Hyperbolic cosine (and its derivatives). */
    static Scalar cosh(Scalar x, int n)
    {
      Scalar res;
      switch (n % 2) {
      case 0:
	res = std::cosh(x);
	break;
      case 1:
	res = std::sinh(x);
	break;
      }
      return res;
    }

    /** \brief Hyperbolic sine (and its derivatives). */
    static Scalar sinh(Scalar x, int n)
    {
      Scalar res;
      switch (n % 2) {
      case 0:
	res = std::sinh(x);
	break;
      case 1:
	res = std::cosh(x);
	break;
      }
      return res;
    }

}; // end of class StdStemFunctions

} // end namespace Eigen

#endif // EIGEN_STEM_FUNCTION