[Ecls-list] About unread-char and bidirectional streams

[Juan Jose Garcia-Ripoll]

On Thu, Jan 1, 2009 at 3:21 PM, Geo Carncross <geocar at gmail.com> wrote:
> My thinking is that ECL is wrong; Consider a bidirectional stream; what
> should write-char do after a unread-char? I think it should clobber the
> character read

It does so right now. I will upload the patches soon :-)

> (with-open-file (s "foo.txt" :direction :io :if-exists :supersede)
 (write-line (print "abcdefghijk") s)
 (file-position s 0)
 (let (a)
   (print (list (file-position s)
                (setf a (read-char s))
                (file-position s)
                (unread-char a s)
                (file-position s)
                (prog1 (write-char #\x s) (finish-output s))
                (file-position s)
                (read-char s)
                (file-position s)
                (read-char s))))
 (file-position s 0)
 (print (read-line s)))

"abcdefghijk"
(0 #\a 1 NIL 0 #\x 1 #\b 2 #\c)
"xbcdefghijk"
"xbcdefghijk"
> (with-open-file (s "foo.txt" :direction :io :if-exists :supersede)
 (write-line (print "ßçéî") s)
 (file-position s 0)
 (let (a)
   (print (list (file-position s)
                (setf a (read-char s))
                (file-position s)
                (unread-char a s)
                (file-position s)
                (prog1 (write-char #\ç s) (finish-output s))
                (file-position s)
                (read-char s)
                (file-position s)
                (read-char s))))
 (file-position s 0)
 (print (read-line s)))

"ßçéî"
(0 #\U00df 2 NIL 0 #\U00e7 2 #\U00e7 4 #\U00e9)
"ççéî"
"ççéî"

-- 
Instituto de Física Fundamental, CSIC
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