// @(#)root/mathmore:$Id: GSLFunctionAdapter.h 20882 2007-11-19 11:31:26Z rdm $
// Authors: L. Moneta, A. Zsenei   08/2005 

 /**********************************************************************
  *                                                                    *
  * Copyright (c) 2004 ROOT Foundation,  CERN/PH-SFT                   *
  *                                                                    *
  * This library is free software; you can redistribute it and/or      *
  * modify it under the terms of the GNU General Public License        *
  * as published by the Free Software Foundation; either version 2     *
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  * This library is distributed in the hope that it will be useful,    *
  * but WITHOUT ANY WARRANTY; without even the implied warranty of     *
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU   *
  * General Public License for more details.                           *
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  * You should have received a copy of the GNU General Public License  *
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  * to the Free Software Foundation, Inc., 59 Temple Place, Suite      *
  * 330, Boston, MA 02111-1307 USA, or contact the author.             *
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  **********************************************************************/

// Header file for class GSLFunctionAdapter
//
// Generic adapter for gsl_function signature 
// usable for any c++ class which defines operator( ) 
// 
// Created by: Lorenzo Moneta  at Fri Nov 12 16:58:51 2004
// 
// Last update: Fri Nov 12 16:58:51 2004
// 
#ifndef ROOT_Math_GSLFunctionAdapter
#define ROOT_Math_GSLFunctionAdapter


namespace ROOT {
namespace Math {

  /**
     Function pointer corresponding to gsl_function signature
   */

  typedef double ( * GSLFuncPointer ) ( double, void *);


  /**
     Class for adapting any C++ functor class to C function pointers used by GSL. 
     The templated C++ function class must implement: 

    <em> double operator( double x)</em>
    and if the derivatives are required: 
    <em> double Gradient( double x)</em>
    
    This class defines static methods with will be used to fill the 
    \a gsl_function and \a gsl_function_fdf structs used by GSL. 
    See for examples the <A HREF="http://www.gnu.org/software/gsl/manual/gsl-ref_32.html#SEC432">GSL online manual</A>
  */ 
     

  template<class UserFunc> 
  class GSLFunctionAdapter {

  public: 

    GSLFunctionAdapter() {}
    virtual ~GSLFunctionAdapter() {} 
    
    static double F( double x, void * p) { 
      
      UserFunc * function = reinterpret_cast< UserFunc *> (p);       
      return (*function)( x ); 
    }

    
    static double Df( double x, void * p) { 
      
      UserFunc * function = reinterpret_cast< UserFunc *> (p);       
      return (*function).Derivative( x ); 
    }

    static void Fdf( double x, void * p, double *f, double *df ) { 
      
      UserFunc * function = reinterpret_cast< UserFunc *> (p);      
      *f  = (*function) ( x ); 
      *df = (*function).Derivative( x ); 
    }

  };


} // namespace Math
} // namespace ROOT


#endif /* ROOT_Math_GSLFunctionAdapter */