NumericalDerivative.h

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#ifndef GAUDIMATH_NUMERICALDERIVATIVE_H
#define GAUDIMATH_NUMERICALDERIVATIVE_H 1
// ============================================================================
// Include files
// ============================================================================
// GaudiKernel
// ============================================================================
#include "GaudiKernel/StatusCode.h"
// ============================================================================
// CLHEP
// ============================================================================
#include "CLHEP/GenericFunctions/AbsFunction.hh"
// ============================================================================

namespace Genfun
{
  namespace GaudiMathImplementation
  {
    class GAUDI_API NumericalDerivative : public AbsFunction
    {
    public:
      enum Type
        { Central  ,
          Forward  ,
          Backward } ;
    public:
      FUNCTION_OBJECT_DEF( NumericalDerivative )

    public:

      NumericalDerivative
      ( const AbsFunction&   function          ,
        const size_t         index             ,
        const Type&          type    = Central ) ;

      NumericalDerivative
      ( const NumericalDerivative&   right    ) ;

      virtual ~NumericalDerivative () = default;

      virtual unsigned int dimensionality() const { return m_DIM ; }

      virtual double operator() ( double          argument ) const ;
      virtual double operator() ( const Argument& argument ) const ;

      virtual bool hasAnalyticDerivative() const { return true ;}

      virtual Derivative partial ( unsigned int index ) const;

    public:

      const AbsFunction&  function () const { return *m_function ; }
      size_t              index    () const { return  m_index    ; }
      const Type&         type     () const { return  m_type     ; }

      const Type&         setType  ( const Type& value );

      double              result   () const { return m_result    ; }
      double              error    () const { return m_error     ; }

    protected:

      StatusCode Exception
      ( const std::string& message                       ,
        const StatusCode&  sc      = StatusCode::FAILURE ) const ;

    private:

      // default constructor  is disabled
      NumericalDerivative ();
      // assignement operator is disabled
      NumericalDerivative& operator=( const NumericalDerivative& ) ;

    private:
      std::unique_ptr<const AbsFunction> m_function  ;
      size_t             m_index     ;
      size_t             m_DIM       ;
      Type               m_type      ;
      //
      mutable Argument   m_argument  ;
      mutable double     m_result    ;
      mutable double     m_error     ;
    };

  } // end of namespace GaudiMathImplementation
} // end of namespace GenFun

// ============================================================================
// The END
// ============================================================================
#endif // GAUDIMATH_NUMERICALDERIVATIVE_H
// ============================================================================