[no subject]

[EB@MIT-ML]

C) TYIPEEK

   The SFA should return a fixnum (as in TYI) but should not remove the
character from the input flow.  Therefore, subsequent TYIPEEK's will read
the same character.  If the SFA cannot handle TYIPEEK, it will be simulated
by a TYI/UNTYI pair of operations.

In LISP 2033:

(setq sfa (sfa-create '(lambda (sfa op val)
			   (caseq op
			      (which-operations '(tyi untyi))
			      (tyi 0)
			      (untyi 0)
			      (t (error)))) 0 'sfa))
#SFA-...
(tyi sfa) 
0  ; so far so good
(tyipeek nil sfa)
; (NIL TYI NIL) ATTEMPT TO INVOKE SFA ON UNSUPPORTED OPERATION 
;  -- or some such error