The alternative gridloop1 code (2)

  _pyfunc_ptr = func1;  /* store func1 for use in _pycall */

  /* allocate help array for creating a double pointer: */
  app = (double **) malloc(nx*sizeof(double*));
  ap = (double *) a->data;
  for (i = 0; i < nx; i++) { app[i] = &(ap[i*ny]); }
  xp = (double *) xcoor->data;
  yp = (double *) ycoor->data;
  gridloop1_C(app, xp, yp, nx, ny, _pycall);
  free(app);
  return Py_BuildValue("");  /* return None */
}