(de sub (filo . fili)(de eof ()
(cond ((null fili)(status 1 20)(status 2 10)(input)(output)
(remprop 'eof 'expr)(reset))(t (input (nextl fili))
(while t (print (substx (read)))(terpri)))))
(output ['dsk (cons filo 'vli)])(status 2 20)(eof)))))))))
(de substx (x)(if (atom x)(if (eq x 'x) '-x x)
 (cons (substx (car x))(substx (cdr x))))))
)))))))))