Crash out of While function

[dwbrink]

How can I cleanly exit a "while" function used with "ssget"? I thought an empty return would work but it exits the whole routeen. If I give give the "while" a fixed exit the routeen works fine. It crashes out befor the list is written to a txt file. Thanks for any help.
See below

(defun c:BB ()
(setq ss x)
(Setvar "osmode" 0)
(setq infolst nil)
(setq T1 1)

(while (/= ss nil)

(Prompt "Pick Dimension")
    (setq SS (ssget))
    (setq elst1 (entget(ssname SS 0)))
    (setq P1 (cdr(assoc 11 elst1)))

    (setq p2 (list (+ (car p1) 0.55)(+ (cadr p1) 0.38) 0.0))
    (setq p3 (list (- (car p2) 0.10)(- (cadr p2) 0.10) 0.0))
    (command "circle" P2 0.25 "")
    
    (setq T2 (itoa T1))
    (command "text" P3 "0.180" "0" T2)

    (setq D1 (cdr(assoc 42 elst1)))
    (setq D1 (rtos D1 2 3))
    (setq INFOLST (append INFOLST (list D1)))
    (setq T1 (1+ T1))

);while

;Write INFOLST out to file

 (setq R (length INFOLST)
       FN "c:\\cad\\Iso9000.txt"
       I 0
      TEX (open FN "w")
 )
      (repeat R
          (setq L (nth I INFOLST))
          (write-line L TEX)
          (setq I (1+ I))
       )
(close TEX)


   
(princ)
)
(princ)

Moderator Note:

Please use [ CODE ] tags...

[aaronic_abacus]

If SS is nil it will not work in other functions.

ie: (setq elst1 (entget(ssname SS 0)))

(ssname nil 0) will crash.

Use:

(if (/= ss nil) (progn...

[RobertB]

Use:
(if (/= ss nil) (progn...

That's a bit silly. Use:
(if ss (progn ...

[aaronic_abacus]

;This autolisp program is a revision of your posted code.
;It works now!

(defun c:BB ()
(setq ss 1)
(Setvar "osmode" 0)
(setq infolst nil)
(setq T1 1)

(while (/= ss nil)

(Prompt "Pick Dimension")
(setq SS (ssget))
(if (/= ss nil) (progn;kind of funny hehe!***********************************************************************


(setq elst1 (entget(ssname SS 0)))
(setq P1 (cdr(assoc 11 elst1)))

(setq p2 (list (+ (car p1) 0.55)(+ (cadr p1) 0.3) 0.0))
(setq p3 (list (- (car p2) 0.10)(- (cadr p2) 0.10) 0.0))
(command "circle" P2 0.25 "")

(setq T2 (itoa T1))
(command "text" P3 "0.180" "0" T2)

(setq D1 (cdr(assoc 42 elst1)))
(setq D1 (rtos D1 2 3))
(setq INFOLST (append INFOLST (list D1)))
(setq T1 (1+ T1))
));end progn/if

);while

;Write INFOLST out to file

(setq R (length INFOLST))
(setq FN "c:\\cad\\Iso9000.txt")
(setq I 0)
(setq TEX (open FN "w"))

(repeat R
(setq L (nth I INFOLST))
(write-line L TEX)
(setq I (1+ I))
)
(close TEX)



(princ)
)
(princ)

[irneb]

What Robert meant was that (/= ss nil) is the same as saying ss. E.g.

(defun c:BB    ()
    (setq ss 1)
    (Setvar "osmode" 0)
    (setq infolst nil)
    (setq T1 1)
    (while ss ;Does the same as (/= ss nil)
        (Prompt "Pick Dimension")
        ;| (setq SS (ssget))
        (if    (/= ss nil)
        Can be replaced with the following line - one step only
        |;
        (if (setq SS (ssget))
            (progn
                (setq elst1 (entget (ssname SS 0)))
                (setq P1 (cdr (assoc 11 elst1)))

                (setq p2 (list (+ (car p1) 0.55) (+ (cadr p1) 0.3) 0.0))
                (setq p3 (list (- (car p2) 0.10) (- (cadr p2) 0.10) 0.0))
                (command "circle" P2 0.25 "")

                (setq T2 (itoa T1))
                (command "text" P3 "0.180" "0" T2)

                (setq D1 (cdr (assoc 42 elst1)))
                (setq D1 (rtos D1 2 3))
                (setq INFOLST (append INFOLST (list D1)))
                (setq T1 (1+ T1))
            ) ;_ end of progn
        );_end of if
    );_end of while
    ;;Write INFOLST out to file
    (setq R (length INFOLST))
    (setq FN "c:\\cad\\Iso9000.txt")
    (setq I 0)
    (setq TEX (open FN "w"))

    (repeat    R
        (setq L (nth I INFOLST))
        (write-line L TEX)
        (setq I (1+ I))
    ) ;_ end of repeat
    (close TEX)

    (princ)
) ;_ end of defun
(princ)

[dwbrink]

Many Many thanks. Very clean solutions. I clearly had not thougth that one through. Again thanks to all!!