GNU bug report logs - #10627
char-ready? is broken for multibyte encodings

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Package: guile;

Reported by: Mark H Weaver <mhw <at> netris.org>

Date: Sat, 28 Jan 2012 10:24:02 UTC

Severity: normal

Done: Andy Wingo <wingo <at> pobox.com>

Bug is archived. No further changes may be made.

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From: Andy Wingo <wingo <at> pobox.com>
To: Mark H Weaver <mhw <at> netris.org>
Cc: 10627 <at> debbugs.gnu.org
Subject: bug#10627: char-ready? is broken for multibyte encodings
Date: Sun, 24 Feb 2013 20:11:50 +0100

On Sat 28 Jan 2012 11:21, Mark H Weaver <mhw <at> netris.org> writes:

> The R5RS specifies that if 'char-ready?' returns #t, then the next
> 'read-char' operation is guaranteed not to hang.  This is not currently
> the case for ports using a multibyte encoding.
>
> 'char-ready?' currently returns #t whenever at least one _byte_ is
> available.  This is not correct in general.  It should return #t only if
> there is a complete _character_ available.

This procedure is omitted in the R6RS because it is not a good
interface.  Besides its semantic difficulties, can you think of a sane
implementation for multibyte characters?

I suggest we document that this procedure only works correctly in
encodings with 1-byte characters and recommend that people use u8-ready?
instead.

Andy
-- 
http://wingolog.org/
This bug report was last modified 8 years and 340 days ago.

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