bug#10627: char-ready? is broken for multibyte encodings

[Andy Wingo]

On Sat 28 Jan 2012 11:21, Mark H Weaver <address@hidden> 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
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