pushback
F->set[F->setcnt] = F->set[F->pushback];
F->set[F->pushback] = tmp;
F->pushback = F->setcnt;
u_long pushback; /* line on the stack */
pushback(COMMA);
pushback(COMMA);
pushback(COMMA);
pushback(*k);
extern void pushback(int);
pushback(t);
pushback(*--token);
pushback(l = gpbc());
pushback(l);
pushback(l);
pushback(digits[num % base]);
pushback('0');
pushback('-');
pushback(n % 10 + '0');