SFAs are almost as much fun as HUNKs!

[ALAN at MIT-MC (Alan Bawden)]

In a bare lisp 1914 the following dialog took place:

;;;An SFA that simply passes its output on to someone else:
(defun foo-function (foo op arg) 
  (caseq op
	 (tyo ((lambda (f) 
		 (cond ((or (< arg 0) (> arg 177))
			(tyo 133 f)	;strange negative numbers are printed
			(prin1 arg f)	;enclosed in square brackets.
			(tyo 135 f))
		       (t (tyo arg f))))
	       (sfa-get foo 0)))
	 (which-operations '(tyo))))
FOO-FUNCTION 

;;;Make one:
(setq foo (sfa-create 'foo-function '1 '|Foo|))
#SFA-|Foo|-70740 

;;;Stuff it with someone to talk to:
(sfa-store foo 0 tyo)
#FILE-OUT-|TTY:* *|-70014 

(setq terpri t)			;just to be sure (the default these days)
T 

(print '(a b c) foo)
(A B C)				;looks fine
T 

(setq terpri nil)		;used to be the default
NIL 

(print '(a b c) foo)
[-4]A [-3]B [-4]C)		;well, there are the funny negative numbers
T				;but where is my open paren??

;;;If I remove the code to print the square bracketed negative numbers
;;;then the open parens come back.