tan.hh

/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
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/*   This file is part of the C++-library RFFGen.                              */
/*   Copyright 2015 Lars Lubkoll                                               */
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#ifndef RFFGEN_CMATH_TAN_HH
#define RFFGEN_CMATH_TAN_HH

#include <cmath>
#include "../Util/base.hh"
#include "../Util/chainer.hh"

namespace RFFGen
{
  namespace CMath
  {
    struct Tan : Base , Chainer<Tan>
    {
      using Chainer<Tan>::operator ();
      explicit Tan(double x=0.) { update(x); }

      void update(double x)
      {
        value = ::tan(x);
        firstDerivative = 1 + ( value * value );
      }

      double d0() const noexcept
      {
        return value;
      }

      template < int = -1 >
      double d1(double dx = 1.) const
      {
        return firstDerivative * dx;
      }

      template < int = -1 , int = -1 >
      double d2(double dx = 1., double dy = 1.) const
      {
        return ( 2 * value * firstDerivative ) * dx * dy;
      }

      template < int = -1 , int = -1 , int = -1 >
      double d3(double dx = 1., double dy = 1., double dz = 1.) const
      {
        return 2 * firstDerivative * ( 1 + ( 3 * value * value ) ) * dx * dy * dz;
      }

    private:
      double value = 0., firstDerivative = 1.;
    };

    template <class Function, class = std::enable_if_t<std::is_base_of<Base,Function>::value> >
    auto tan(const Function& f)
    {
      return Tan()(f);
    }
  }
}

#endif // RFFGEN_CMATH_TAN_HH