// $Id: LookupTable.hh,v 1.2 2002/08/18 23:15:01 kamland0 Exp $

#ifndef __LookupTable_hh__
#define __LookupTable_hh__

#include <math.h>

#include "TObject.h"

class TKLLookupTableFixedBin : public TObject {
public:
  TKLLookupTableFixedBin() : fY(0) { }
  virtual ~TKLLookupTableFixedBin() {}

  void Initialize( Int_t nsamp, Double_t xlow, Double_t xhigh,
		   Double_t(*f)(Double_t)=0 );

  void SetPoint( Double_t x, Double_t y );

  inline Double_t Interpolate1( Double_t x );

  inline Double_t Interpolate1( Double_t x, Double_t &dydx );

  // Other interpolations can be added, but linear interpolation is
  // best for many purposes, particularly when memory is cheap enough to
  // allow fine sampling and speed is paramount.
  
protected:
  Int_t fNsamp;
  Double_t fXlow;
  Double_t fDX;  
  Double_t *fY;
  
  ClassDef(TKLLookupTableFixedBin, 1)  // numeric lookup table  
};


inline Double_t TKLLookupTableFixedBin::Interpolate1( Double_t x )
{
  // linear interpolation, inlined for speed.  Note linear
  // interpolation is best for many purposes, particularly when memory
  // is cheap enough to allow fine sampling and speed is paramount.
  Double_t di= (x-fXlow)/fDX;
  Int_t i= (Int_t)di;
  if (i<0)
    i=0;
  else if (i>=fNsamp-1)
    i= fNsamp-2;
  di -= i;
  return fY[i] + di * (fY[i+1]-fY[i]);
}

inline Double_t TKLLookupTableFixedBin::Interpolate1( Double_t x,
						      Double_t &dydx )
{
  // linear interpolation with derivative, inlined for speed.  Note linear
  // interpolation is best for many purposes, particularly when memory
  // is cheap enough to allow fine sampling and speed is paramount.
  Double_t di= (x-fXlow)/fDX;
  Int_t i= (Int_t)di;
  if (i<0)
    i=0;
  else if (i>=fNsamp-1)
    i= fNsamp-2;
  di -= i;
  dydx= (fY[i+1]-fY[i])/fDX;
  return fY[i] + di * (fY[i+1]-fY[i]);
}

#endif