numericalIntegrator.h

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// -*- Mode: C++; tab-width: 2; -*-
// vi: set ts=2:
//
// $Id: numericalIntegrator.h,v 1.18 2004/05/27 19:49:42 oliver Exp $
//

#ifndef BALL_MATHS_NUMERICALINTEGRATOR_H
#define BALL_MATHS_NUMERICALINTEGRATOR_H

#ifndef BALL_MATHS_FUNCTION_H
# include <BALL/MATHS/function.h>
#endif

namespace BALL
{ 
  template <typename Function, typename DataType = float>
  class NumericalIntegrator
  {

    public:

    BALL_CREATE(NumericalIntegrator)

    

    
    
    NumericalIntegrator();
    
    NumericalIntegrator(const NumericalIntegrator& nint);
    
    virtual ~NumericalIntegrator();





    NumericalIntegrator& operator = (const NumericalIntegrator& nint);

    
    


    bool operator == (const NumericalIntegrator& nint) const;





    void setFunction(const Function& function);

    const Function& getFunction() const  { return function_; }

    Function& getFunction()  { return function_; }

    DataType getValue(const DataType& x) const;

    DataType integrate(const DataType& from, const DataType& to) const;



    protected:

    //_ The function to be integrated
    Function function_;

  };


  template<typename Function, typename DataType>
  BALL_INLINE
  NumericalIntegrator<Function, DataType>::NumericalIntegrator()
    : function_()
  {
  }


  template<typename Function, typename DataType>
  BALL_INLINE
  NumericalIntegrator<Function, DataType>::NumericalIntegrator(const NumericalIntegrator<Function, DataType>& nint)
    : function_(nint.function_)
  {
  }


  template<typename Function, typename DataType>
  BALL_INLINE
  NumericalIntegrator<Function, DataType>::~NumericalIntegrator()
  {
  }


  template<typename Function, typename DataType>
  BALL_INLINE
  NumericalIntegrator<Function, DataType>&
  NumericalIntegrator<Function, DataType>::operator =
  (const NumericalIntegrator<Function, DataType>& nint)
  {
    function_ = nint.function_;
    return *this;
  }


  template<typename Function, typename DataType>
  BALL_INLINE
  void NumericalIntegrator<Function, DataType>::setFunction(const Function& function)
  { 
    function_ = function;
  }


  template<typename Function, typename DataType>
  BALL_INLINE
  bool NumericalIntegrator<Function, DataType>::operator ==
  (const NumericalIntegrator<Function, DataType>& nint) const
  {
    return (function_ == nint.function_);
  }


  template<typename Function, typename DataType>
  BALL_INLINE
  DataType NumericalIntegrator<Function, DataType>::getValue(const DataType& x) const
  {
    return function_(x);
  }


  template<typename Function, typename DataType>
  BALL_INLINE
  DataType NumericalIntegrator<Function, DataType>::integrate(
      const DataType& from, const DataType& to) const
  {
    // ?????
    // the number of samples has to be user configurable
    Size samples = 30;
    Size n = samples;

    DataType area = 0;
    DataType step = (to - from) / n;
    DataType x = from;

    while (n > 0)
    {
      area += (function_(x) + function_(x + step)) / 2.0 * step;
      x += step;
      --n;
    }

    return area;
  }
}

#endif // BALL_MATHS_NUMERICALINTEGRATOR_H

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