From: Neil Jerram <neil@ossau.uklinux.net>
To: Andy Wingo <wingo@pobox.com>
Cc: guile-devel <guile-devel@gnu.org>
Subject: Re: truth of %nil
Date: Mon, 29 Jun 2009 22:44:54 +0100 [thread overview]
Message-ID: <87k52uvhnt.fsf@arudy.ossau.uklinux.net> (raw)
In-Reply-To: <m33a9izqvo.fsf@pobox.com> (Andy Wingo's message of "Mon\, 29 Jun 2009 23\:12\:11 +0200")
Andy Wingo <wingo@pobox.com> writes:
> Hi all,
>
> Daniel came up with an interesting test case:
>
> scheme@(guile-user)> (if %nil 1 2)
> 1
>
> We could fix this transparently by changing scm_is_false in boolean.h
> from:
>
> #define scm_is_false(x) scm_is_eq ((x), SCM_BOOL_F)
>
> to
>
> #define scm_is_false(x) (scm_is_eq ((x), SCM_BOOL_F) || SCM_NILP (x))
>
> I'm not really sure if this is the right place for this to go, though.
> It seems that it is. (Ideally the two values would differ by one bit
> only, and we could mask that bit away and just have the one test.) What
> do people think?
>
> Andy
> --
> http://wingolog.org/
Seems wrong to me. In Scheme #f should be the only false value.
What's the argument for %nil being false in Scheme code?
Neil
next prev parent reply other threads:[~2009-06-29 21:44 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-06-29 21:12 truth of %nil Andy Wingo
2009-06-29 21:44 ` Neil Jerram [this message]
2009-06-29 22:11 ` Andy Wingo
2009-06-30 22:22 ` Neil Jerram
2009-07-01 6:45 ` Daniel Kraft
2009-07-01 21:54 ` Neil Jerram
2009-07-05 13:07 ` Mark H Weaver
2009-08-30 11:07 ` Neil Jerram
2009-08-30 14:11 ` Mark H Weaver
2009-09-01 22:00 ` Neil Jerram
2009-09-02 15:57 ` Mark H Weaver
2009-09-17 21:21 ` Neil Jerram
2009-07-02 14:28 ` Mark H Weaver
2009-07-02 14:50 ` Ludovic Courtès
2009-07-02 22:50 ` Neil Jerram
2009-07-03 15:32 ` Mark H Weaver
2009-07-05 2:41 ` Mark H Weaver
2009-07-05 9:19 ` Andy Wingo
2009-07-07 11:14 ` Mark H Weaver
2009-07-08 13:17 ` Mark H. Weaver
2009-08-30 11:20 ` Neil Jerram
2009-08-30 11:13 ` Neil Jerram
2009-08-30 14:15 ` Mark H Weaver
2009-09-01 21:50 ` Neil Jerram
2009-08-30 22:01 ` Ken Raeburn
2009-08-31 21:59 ` Ludovic Courtès
2009-08-31 23:39 ` Ken Raeburn
2009-08-31 21:55 ` SCM_BOOL_F == 0 and BDW-GC Ludovic Courtès
2009-09-17 22:00 ` Neil Jerram
2009-09-17 22:28 ` Ludovic Courtès
2009-09-18 20:51 ` Neil Jerram
2009-09-20 17:21 ` Ludovic Courtès
2009-09-20 21:03 ` Neil Jerram
2009-09-20 21:36 ` Ludovic Courtès
2009-07-06 21:46 ` truth of %nil Neil Jerram
2009-07-06 23:54 ` Mark H Weaver
2009-07-08 8:08 ` Ludovic Courtès
2009-07-23 21:12 ` Andy Wingo
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