From: Mark H Weaver <mhw@netris.org>
To: David Kastrup <dak@gnu.org>
Cc: 17296@debbugs.gnu.org
Subject: bug#17296: Uh, wrong?
Date: Tue, 03 Jun 2014 22:55:42 -0400 [thread overview]
Message-ID: <87a99tv0wh.fsf@yeeloong.lan> (raw)
In-Reply-To: <87wqcx99zk.fsf@fencepost.gnu.org> (David Kastrup's message of "Tue, 03 Jun 2014 19:30:23 +0200")
David Kastrup <dak@gnu.org> writes:
> So the behavior for length+ on a dotted list is strictly unspecified.
> It is not even stated "it is an error".
Actually, it is. At the end of the section that defines the "types"
such a "clist" and "flist", it states:
It is an error to pass a circular or dotted list to a procedure not
defined to accept such an argument.
While it is true that we are not required to signal an error, I'm wary
extending 'length+' in this way. It also effectively extends 'map' and
'for-each' to support things like (map + '() 'foo), and thus potentially
affects many other procedures both inside and outside of Guile that use
'map' and 'for-each'. Once we've done this, users are likely to grow
dependent on it and we can never go back.
> At any rate, what I am getting at is that I was going to submit the
> following patch as a part of a series fixing other bugs, bugs that I
> need a working "get the length of a dotted list" operator for. We don't
> have any such operator in GUILE, and that's awkward.
It might be helpful to add such a procedure, but I don't think 'length+'
should be it.
Regards,
Mark
next prev parent reply other threads:[~2014-06-04 2:55 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-18 19:26 bug#17296: [PATCH] SRFI-1 'length+' raises an error unless passed a proper or circular list Mark H Weaver
2014-06-02 0:56 ` Mark H Weaver
2014-06-03 17:30 ` bug#17296: Uh, wrong? David Kastrup
2014-06-04 2:55 ` Mark H Weaver [this message]
2014-06-04 4:39 ` David Kastrup
2014-06-04 14:49 ` Mark H Weaver
2014-09-22 17:34 ` Mark H Weaver
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