对话框下拉按钮程式的问题!

tyliling

各位，我写了一个小程序，用到了DCL的下拉对话框，程式的一部份如下所示:

(defun sub_ppp(vvs)
 (cond ((= ppp 5) (setq oldpop (get_tile "pop"))
                  (setq newpop (nth (atoi vvs) plotname))
                  (set_tile "pop" (strcat oldpop newpop))
           (setq acadtool (nth (atoi (setq pop (get_tile "pop"))) plotname))
           )
  
      ((= ppp 6) (setq oldacad (get_tile "acad"))
                 (setq newacad (nth (atoi vvs) plotstyle))
                 (set_tile "acad" (strcat oldacad newacad))
                 (setq output (nth (atoi (setq acad (get_tile "acad"))) plotstyle))
                 )
      ((= ppp 7) (setq oldpapre1 (get_tile "papre1"))
                 (setq newpapre1 (nth (atoi vvs) plotpapre1))
                 (set_tile "papre1" (strcat oldpapre1 newpapre1))
                 (setq size1 (nth (atoi (setq papre1 (get_tile "papre1"))) plotpapre1))
                 )
       ((= ppp 8) (setq oldpapre2 (get_tile "papre2"))
                 (setq newpapre2 (nth (atoi vvs) plotpapre2))
                 (set_tile "papre2" (strcat oldpapre2 newpapre2))
                 (setq size2 (nth (atoi (setq papre2 (get_tile "papre2"))) plotpapre2))
                 )
    
  )
  )

比如我现在的ppp =6时执行到 (atoi vvs )时就出现如下错误不知怎么回事.

; error: bad argument type: consp nil

请高手指教一下

sieben

把全部代码贴出来,包括DCL代码,要不检查一下 oldacad    plotstyle 两个变量的值