nullstelle.h

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#ifndef _NULLSTELLE_
#define _NULLSTELLE_
 
#include <exception>
#include <math.h>
#include "backend/exceptions.h"
 
namespace dg{
 
class NoRoot1d: public std::exception
{
  private:
    double x1, x2, wert_min, wert_max;
  public:
    NoRoot1d(double x_min, double x_max, double wert_min, double wert_max): x1(x_min), x2(x_max), wert_min(wert_min), wert_max(wert_max){}
    void display() const
    {
      std::cerr << "Between " <<x1<<"/"<<wert_min << " and "<<x2<<"/"<<wert_max<<" is no root!\n";
    }
    char const* what() const throw(){ return "There is no root!";}
};
 
template <typename UnaryOp>
int bisection1d (UnaryOp& op, double& x_min, double& x_max, const double eps)
{
    double  mitte;
    double wert_max, wert_mitte, wert_min;
    wert_max=op(x_max);
    wert_min=op(x_min);
 
    if(wert_max*wert_min>=0)
        throw NoRoot1d(x_min, x_max, wert_min, wert_max);
 
    int j_max = 60;
    for(int j=0; j<j_max; j++)
    {
        wert_mitte = op( mitte =(x_min+x_max)/2.0 );
        if(wert_mitte==0)               {x_min=x_max=mitte; return j+3;}
        else if(wert_mitte*wert_max>0)  x_max = mitte;
        else                            x_min = mitte;
        if( fabs(x_max-x_min)<eps*fabs(x_max) + eps)         return j+3;
    }
    throw std::runtime_error("Too many steps in root finding!");
}
 
}//namespace dg
#endif //_NULLSTELLE_