1  typedef struct x
       2  {
       3    struct x *type;
       4    struct x *chain;
       5    struct x *value;
       6  } *tree;
       7  
       8  int
       9  func (new, old)
      10       register tree new, old;
      11  {
      12    if (old->type == 0 || new->type == 0)
      13      {
      14        register tree t = old->type;
      15        if (t == 0)
      16  	t = new->type;
      17        for (; t; t = t->chain )
      18  	if (t->value)
      19  	  return 1;
      20      }
      21    return 0;
      22  }