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bug#12216: peek-char incorrectly *CONSUMES* eof

From: Andy Wingo
Subject: bug#12216: peek-char incorrectly *CONSUMES* eof
Date: Thu, 07 Mar 2013 22:32:38 +0100
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/24.2 (gnu/linux)

On Tue 05 Mar 2013 20:17, "David A. Wheeler" <address@hidden> writes:

> I reported:
>> > Guile's peek-char has a bug; it incorrectly *consumes* eof instead of
>> > just reporting it.
> Andy Wingo replied:
>> I have the feeling that for interactive use, if you expect to read a EOF
>> from a port and then continue, you have to not use peek-char.  You need
>> to handle your own lookahead buffer.  I know it's not a great answer,
>> but I can't think of anything else that makes sense.
> We don't want to read an EOF and then continue.
> We peek-char to not *CONSUME* an interactive EOF.

I understand what it is you want.  But I don't know of any sane way to
implement it.

Given that it is an edge case -- peek-char on an interactive port -- I
think the thing to do is to document this inconsistency, and for you (in
your code) to implement some sort of abstraction that does not use

That is to say, use read-char, and do unread-char as necessary.  Or keep
your own buffer around.

I know it isn't nice, but I don't know how to do anything better.


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