/* 1 -1 sum of the defined cells
*/

#define SUM_SUM d[0]

static void rf_sum_callback( Data *d)
{
  if( debug) fprintf( out, "sum += %g\n", d->list_val);

  d->SUM_SUM += d->list_val;
}

double rf_sum(const Node *n, const Cell *c)
{
  Data d;  d.SUM_SUM = 0;

  ss_traverse_list( Right(n), c, rf_sum_callback, &d);

  return d.SUM_SUM;
}