From: Mark H Weaver <mhw@netris.org>
To: ludo@gnu.org (Ludovic Courtès)
Cc: rain1@openmailbox.org, 20087@debbugs.gnu.org
Subject: bug#20087: gensym
Date: Wed, 23 Mar 2016 13:55:13 -0400 [thread overview]
Message-ID: <87twjxqdtq.fsf@netris.org> (raw)
In-Reply-To: <87wpovueos.fsf@gnu.org> ("Ludovic \=\?utf-8\?Q\?Court\=C3\=A8s\=22'\?\= \=\?utf-8\?Q\?s\?\= message of "Tue, 22 Mar 2016 08:58:27 +0100")
ludo@gnu.org (Ludovic Courtès) writes:
> Mark H Weaver <mhw@netris.org> skribis:
>
>> If we cannot eliminate the possibility of collisions, and we cannot
>> avoid intentional collisions, what can we do? I think the best we can
>> hope for is to significantly reduce the probability of _unintentional_
>> collisions, perhaps by starting the gensym counter at a large number.
>
> I’m not sure if that would help.
>
> One thing that could help avoid unintentional collisions is to
> automatically add whitespace before the number, such that:
>
> (gensym "x") => #{x 123}#
I think this is a good idea.
>> The other thing we can do is to clearly document these inherent problems
>> with gensym, so that they will not be misused for jobs for which they
>> are not appropriate.
>
> I think we should add a sentence to that effect in the manual.
It turns out the manual already has the following text in the ‘gensym’
entry, which I think is sufficient.
The symbols generated by ‘gensym’ are _likely_ to be unique, since
their names begin with a space and it is only otherwise possible to
generate such symbols if a programmer goes out of their way to do so.
Uniqueness can be guaranteed by instead using uninterned symbols
(*noteSymbol Uninterned::), though they can’t be usefully written out
and read back in.
What do you think?
Mark
next prev parent reply other threads:[~2016-03-23 17:55 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-11 17:15 bug#20087: 'gensym' is not guaranteed to return a fresh symbol Ludovic Courtès
2016-03-18 17:03 ` bug#20087: gensym rain1
2016-03-22 5:24 ` Mark H Weaver
2016-03-22 7:58 ` Ludovic Courtès
2016-03-23 17:55 ` Mark H Weaver [this message]
2016-03-24 8:45 ` Ludovic Courtès
2016-06-23 13:48 ` Andy Wingo
2016-06-23 14:13 ` Ludovic Courtès
2016-06-23 16:05 ` Andy Wingo
2016-03-22 11:21 ` rain1
2016-03-22 18:06 ` Mark H Weaver
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