From: ludovic.courtes@laas.fr (Ludovic Courtès)
Cc: hanwen@xs4all.nl, guile-devel@gnu.org
Subject: Re: Backtrace and enhanced catch
Date: Mon, 16 Jan 2006 09:38:47 +0100 [thread overview]
Message-ID: <87hd84pnxk.fsf@laas.fr> (raw)
In-Reply-To: <87acebhf1o.fsf@ossau.uklinux.net> (Neil Jerram's message of "Wed, 04 Jan 2006 21:13:55 +0000")
Hi,
Better late than never... ;-)
Neil Jerram <neil@ossau.uklinux.net> writes:
> Another (lesser) problem with lazy-catch and with-exception-handler is
> that they are always used in practice in a particular pattern. For
> lazy-catch the pattern is
>
> (catch tag
> (lambda ()
> (lazy-catch tag thunk lazy-handler))
> catch-handler)
>
> For with-exception-handler the pattern (as shown by all the examples
> in SRFI-34) is
>
> (call/cc
> (lambda (k)
> (with-exception-handler
> (lambda (obj)
> ...
> (k 'exception))
> thunk)))
>
> Why is this a problem? Because it strongly suggests that these forms
> are more general than is useful. And there is a cost to this: a bit
> more typing in Scheme, and in the case of Guile a lot more complexity
> in the C code needed to set up a catch and lazy catch pair (which is
> relevant to the backtrace problem).
OTOH, this would suggest that `lazy-catch' and `call/cc' are all we need
to implement `catch'. This is probably the reason why SRFI-34 defines
no construct equivalent to `catch'.
>From a theoretical viewpoint, it seems to me that it would make sense to
just keep `lazy-catch' as a primitive and have `catch' implemented as a
macro on top of it. Now, from Guile's implementation viewpoint, I guess
it would be much more costly/complex as you said.
Anyway, thanks for your patch: it's nice to see this issue is going to
be fixed! ;-) And sorry for not replying earlier.
Ludovic.
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next prev parent reply other threads:[~2006-01-16 8:38 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-12-01 0:16 gh_inexact_p error in 1.7.x Bruce Korb
2005-12-01 0:44 ` Kevin Ryde
2005-12-05 4:08 ` No way out Bruce Korb
2005-12-05 4:35 ` Bruce Korb
2005-12-07 1:31 ` Marius Vollmer
2005-12-05 22:20 ` Kevin Ryde
2005-12-06 10:58 ` Han-Wen Nienhuys
2005-12-28 15:59 ` Neil Jerram
2005-12-31 15:09 ` Han-Wen Nienhuys
2005-12-31 15:14 ` Neil Jerram
2006-01-01 19:58 ` Han-Wen Nienhuys
2006-01-02 15:42 ` Neil Jerram
2006-01-02 18:54 ` Neil Jerram
2006-01-04 21:13 ` Backtrace and enhanced catch Neil Jerram
2006-01-14 12:41 ` Neil Jerram
2006-01-22 13:47 ` Marius Vollmer
2006-01-23 20:11 ` Neil Jerram
2006-01-24 21:34 ` Marius Vollmer
2006-01-16 8:38 ` Ludovic Courtès [this message]
2006-01-18 23:08 ` Neil Jerram
2006-01-19 9:38 ` Ludovic Courtès
2006-01-21 11:26 ` Neil Jerram
2006-01-26 23:29 ` Kevin Ryde
2006-01-27 19:30 ` Neil Jerram
2006-01-31 20:07 ` Kevin Ryde
2006-02-01 23:04 ` Neil Jerram
2006-02-04 0:46 ` Kevin Ryde
2006-02-04 15:41 ` Neil Jerram
2005-12-07 1:07 ` No way out Marius Vollmer
2005-12-07 1:55 ` Rob Browning
2005-12-13 20:32 ` Marius Vollmer
2005-12-28 16:09 ` Neil Jerram
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