Re: [Sbcl-devel] [PATCH] peek-char-wrongly-echos-to-echo-stream

[Raymond T. <to...@rt...>]

>>>>> "Matthew" == Matthew Danish <md...@an...> writes:

    Matthew> +
    Matthew>  (defun echo-misc (stream operation &optional arg1 arg2)
    Matthew>    (let* ((in (two-way-stream-input-stream stream))
    Matthew>  	 (out (two-way-stream-output-stream stream)))
    Matthew> @@ -990,6 +1016,20 @@
    Matthew>  	     in-type `(and ,in-type ,out-type))))
    Matthew>        (:close
    Matthew>         (set-closed-flame stream))
    Matthew> +      (:peek-char
    Matthew> +       ;; For the special case of peeking into an echo-stream
    Matthew> +       ;; arg1 is peek-type, arg2 is (eof-error-p eof-value)
    Matthew> +       ;; returns peeked-char, eof-value, or errors end-of-file
    Matthew> +       (flet ((outfn (c)
    Matthew> +		(if (ansi-stream-p out)
    Matthew> +		    (funcall (ansi-stream-out out) out c)
    Matthew> +		    ;; gray-stream
    Matthew> +		    (stream-write-char out c))))
    Matthew> +	 (generalized-peeking-mechanism
    Matthew> +	  arg1 (second arg2) char
    Matthew> +	  (read-char in (first arg2) (second arg2))
    Matthew> +	  (unread-char char in)
    Matthew> +	  (outfn char))))

While trying to port this patch to CMUCL, I got confused by this
part.  It seems we are still sending output characters to the
out-stream of an echo-stream because generalized-peeking-mechanism
calls (outfn char).  If we're not supposed to send output to
echo-stream, why do we call (outfn char)?

I must be missing something!

Ray