NaN's Paul Schlie (29 Oct 2005 15:50 UTC)
Re: NaN's Marcin 'Qrczak' Kowalczyk (29 Oct 2005 16:39 UTC)
Re: NaN's Paul Schlie (29 Oct 2005 18:22 UTC)
Re: NaN's Marcin 'Qrczak' Kowalczyk (29 Oct 2005 19:14 UTC)
Re: NaN's Paul Schlie (29 Oct 2005 22:49 UTC)
Error objects in general bear (29 Oct 2005 19:46 UTC)
Re: Error objects in general Marcin 'Qrczak' Kowalczyk (29 Oct 2005 20:22 UTC)
Re: Error objects in general bear (30 Oct 2005 05:57 UTC)
Re: Error objects in general Marcin 'Qrczak' Kowalczyk (30 Oct 2005 14:17 UTC)
Re: Error objects in general Alan Watson (29 Oct 2005 21:26 UTC)
Re: Error objects in general bear (30 Oct 2005 05:40 UTC)
Re: Error objects in general Taylor Campbell (30 Oct 2005 05:45 UTC)
Re: Error objects in general bear (30 Oct 2005 06:08 UTC)
Re: Error objects in general Taylor Campbell (30 Oct 2005 16:49 UTC)
Re: Error objects in general Alan Watson (30 Oct 2005 05:54 UTC)
Re: Error objects in general bear (30 Oct 2005 06:07 UTC)
Re: Error objects in general Alan Watson (30 Oct 2005 06:46 UTC)
Re: Error objects in general Paul Schlie (30 Oct 2005 12:39 UTC)
Re: Error objects in general Paul Schlie (30 Oct 2005 13:04 UTC)
Re: Error objects in general John.Cowan (30 Oct 2005 16:30 UTC)
Re: Error objects in general Alan Watson (30 Oct 2005 20:29 UTC)
Re: Error objects in general Alan Watson (30 Oct 2005 13:17 UTC)

Re: Error objects in general Alan Watson 30 Oct 2005 06:46 UTC

bear wrote:
> It's different because #f is a useful value, not a signal that some
> operation failed or was invalid.

#f is often used to signal failure. For examples, look no further than
string->number and assoc.

> In general, operations that are
> supposed to retrieve a value can fail, and then what value do they
> return?

Yup, you've identified one of the oldest problems in interface design.

Alan
--
Dr Alan Watson
Centro de Radioastronomía y Astrofísica
Universidad Astronómico Nacional de México