1typedef struct x 2{ 3 struct x *type; 4 struct x *chain; 5 struct x *value; 6} *tree; 7 8int 9func (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} 23