reiezione, 3

double randFunc(double func(double), 
                double minx, double maxx,
                double miny, double maxy) {
  if (maxx < minx) return maxx - 1 ;
  if (maxy < miny) return minx - 1 ;
  double output = minx - 1 ;
  while (output < minx) {
      double x = randFlat(minx, maxx) ;
      double y = randFlat(miny, maxy*1.0001) ;
      if (func(x) > y) output = x ;      
  }
  return output ;    
}