(DEFUN MAPKAR (FUN FIRST &REST LISTS)
  (PROG (ARGS HEAD TAIL Q A)
        (SETQ LISTS (CONS FIRST LISTS))
        ;; Make a skeleton ARGS list
        (SETQ Q LISTS)
   10   (IF (NULL Q) (GO 20))
        (SETQ ARGS (CONS NIL ARGS))
        (SETQ Q (CDR Q))
        (GO 10)
        ;; Advance all lists and gather the CARs
   20   (SETQ Q LISTS)
        (SETQ A ARGS)
   30   (IF (NULL Q) (GO 40))
        ;; When any of the lists is exhausted, we're done
        (IF (NULL (CAR Q)) (RETURN HEAD))
        (RPLACA A (CAAR Q))
        (RPLACA Q (CDAR Q))
        (SETQ Q (CDR Q) A (CDR A))
        (GO 30)
        ;; Apply the function and gather the result
   40   (SETQ Q (APPLY FUN ARGS))
        (IF TAIL
            (SETQ TAIL (CDR (RPLACD TAIL (CONS Q NIL))))
            (SETQ HEAD (SETQ TAIL (CONS Q NIL))))
        (GO 20)))