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Re: R6RS exception printing at the REPL

From: Ludovic Courtès
Subject: Re: R6RS exception printing at the REPL
Date: Thu, 02 Dec 2010 00:13:10 +0100
User-agent: Gnus/5.110011 (No Gnus v0.11) Emacs/23.2 (gnu/linux)

Hello there!

Andy Wingo <address@hidden> writes:

> On Sat 27 Nov 2010 01:08, Andreas Rottmann <address@hidden> writes:
>> to not lose current functionality, `print-exception' and exception
>> printer procedures would need a `frame' argument as well, right?
> I guess. I never liked that, though; sounds like a needless tangling of
> concerns. What does having the frame give us? Just source, or the
> function name, or what? It seems like a message about the context in
> which the error occurred could just as well come before the error is
> printed out.
> What do you think? What does Ludovic think? :)

I don’t think, actually.  :-)

Well, at first I thought exception printers could be nice.  Currently,
there’s a single exception printer, which makes assumptions about the
arguments to ‘throw’.  Namely, it expects (throw KEY FUNC FORMAT-STRING
FORMAT-ARG ...), or something like that.  When that is honored,
exceptions are displayed in a human-readable way, otherwise they are
(very) badly printed, which could be improved.

OTOH, exceptions are a programming mechanism, not a UI mechanism, so one
could argue that it’s up to the application to define how to present
exceptions to the user.

I think I’m slightly skeptical about system-wide exception printers
because of this, and also because system-wide settings are evil.


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