CachedFunction1D.h

#ifndef CACHEDFUNCTION1D_H
#define CACHEDFUNCTION1D_H

#include <iostream>
#include <cmath>

namespace SctData{

    class CachedFunction1D{
    public:
    CachedFunction1D(double min, double max, double delta, double (*function)(double) ) throw() ;
    ~CachedFunction1D() throw() ;
    inline double eval(double x) const throw() ;
    private:
    CachedFunction1D() throw() ;
    CachedFunction1D& operator=(const CachedFunction1D&) throw() ;
    void makeTable() throw();    
    double min;                  
    double max;                  
    double delta;                
    double invdelta;             
    int nvalue;                  
    double * values;             
    double (*function) (double); 
    };
    
// inline function
    double CachedFunction1D::eval(double x) const throw() {
    /*
    int ipos=(int)((x-min)*invdelta);
    if (ipos<0)            { return values[0];        }
    else if (ipos>=nvalue) { return values[nvalue-1]; }
    else                   { return values[ipos];     }
    */
    double pos = (x-min)*invdelta;
    int ipos=(int)(pos);
    if (ipos<0)            { return values[0];        }
    else if (ipos>=nvalue-1) { return values[nvalue-1]; }
    //interpolate
    double frac = pos - ipos;   
    double y1 = values[ipos];
    double y2 = values[ipos+1];
    //double x1 = ipos * delta + min;
    //double x2 = (ipos+1) * delta + min;
    //cout << x1 << "  "<< x2 << " "  << y1 << "  " << y2 << "  " << x << "  " << pos << "   " << ipos << "  " << frac << "  " << (x-x1)/(x2-x1) << endl;
    return y1 + (y2-y1) * frac;
    }

}



#endif // #ifndef CACHEDFUNCTION_H

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