[r6rs-discuss] Stateful codecs and inefficient transcoding

From: Shiro Kawai <shiro>
Date: Tue Oct 31 01:21:00 2006

From: William D Clinger <will_at_ccs.neu.edu>
Subject: [r6rs-discuss] Stateful codecs and inefficient transcoding
Date: Tue, 31 Oct 2006 00:51:00 -0500

> I am posting this as an individual member of the Scheme
> community. I am not speaking for the R6RS editors.
>
> Marcin 'Qrczak' Kowalczyk wrote:
> > Discussion would be easier if R6RS had proivided a mechanism for
> > implementing codecs or transcoders, which would reveal the protocol
> > used to maintain transcoder state across invocations.
>
> The draft R6RS does not require or envision any
> mutable state in transcoders, nor does it provide or
> require any means for maintaining mutable transcoder
> state across invocations of textual i/o procedures.

Oh, that's where I misunderstood. If a transcoder can have
mutable state, the story is a bit different. But then the
eqv?-ness in the draft sounds weird:

<quote>
A transcoder returned by make-transcoder is equal in the sense
of eqv? to any other transcoder returned by make-transcoder,
if and only if code, eof-style, and handling-mode arguments
are equal in the sense of eqv?
</quote>

This suggests two transcoders are eqv? if created with the
same arguments, even if those two carry different internal
states. Is it really the intention of the authors?

--shiro
Received on Tue Oct 31 2006 - 01:22:32 UTC