StemFunction.h

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// This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2010, 2013 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 { 
 
namespace internal {
 
/** \brief The exponential function (and its derivatives). */
template <typename Scalar>
Scalar stem_function_exp(Scalar x, int)
{
  using std::exp;
  return exp(x);
}
 
/** \brief Cosine (and its derivatives). */
template <typename Scalar>
Scalar stem_function_cos(Scalar x, int n)
{
  using std::cos;
  using std::sin;
  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). */
template <typename Scalar>
Scalar stem_function_sin(Scalar x, int n)
{
  using std::cos;
  using std::sin;
  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). */
template <typename Scalar>
Scalar stem_function_cosh(Scalar x, int n)
{
  using std::cosh;
  using std::sinh;
  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). */
template <typename Scalar>
Scalar stem_function_sinh(Scalar x, int n)
{
  using std::cosh;
  using std::sinh;
  Scalar res;
  
  switch (n % 2) {
  case 0:
    res = std::sinh(x);
    break;
  case 1:
    res = std::cosh(x);
    break;
  }
  return res;
}
 
} // end namespace internal
 
} // end namespace Eigen
 
#endif // EIGEN_STEM_FUNCTION