static void SkipComments(ifstream &input){

  // Look ahead in the input stream
  int c;
  bool cont = true;
  bool comment = false;
  while(cont && !input.eof()){
    c = input.peek();

    // Skip spaces
    if(c == ' ' || c == '\t') input.get();

    // Skip end-of-lines
    else if(c == '\n'){
      input.get();

      // If we were inside a comment, we just finished it.
      comment = false;
    }

    // Skip comments
    else if(c == '#' || comment){
      input.get();

      // We are entering a comment (starting with '#' and finishing
      // with the end of the line).
      comment = true;
    }

    // If the last character found cannot be skipped
    else cont = false;
  }
}


int PbF2Abslen(char *fname){
  double *xx=new double[200];
  double *yy=new double[200];
  int nc;
 ifstream fin(fname);
  if (fin.is_open()){ 
    while (! fin.eof() )
      {

	SkipComments(fin);
	fin >> xx[nc] >>  yy[nc];
	if (fin.eof())break;
	//	cout << "x:" <<  xx[nc] <<" y:" <<   yy[nc]<< endl;
	nc++;
      }   
    fin.close();
  } else {
    cerr << fname <<" cannot be opened! "<< endl;
  }
  TGraph *g=new TGraph(nc,xx,yy);

  nc=0;
  for (double i=340;i<840;i+=10){
    // cout << i << " " << -10/log(g->Eval(i)/100.)<< endl;
    cout << i << " " << g->Eval(i)<< endl;
    xx[nc] = i;
    yy[nc] = g->Eval(i);
    nc++;
  } 
  TGraph *g1=new TGraph(nc,xx,yy);

  TCanvas *c= new TCanvas("c","c",600,600);
  g->Draw("AC*");
  g1->Draw("L");
  c->Modified();
  c->Update();

  return 0;

}