Correction: *asksign* results are supposed to be persistent; *sign* is not
supposed to change the database at all. Calling clearsign from sign to
clear *all* assumptions is wrong. If for some reason sign has the
side-effect of changing the database, that is a bug in sign which needs to
be fixed at the source.
On Fri, Aug 30, 2013 at 1:50 PM, Stavros Macrakis <macrakis at alum.mit.edu>wrote:
> It is clearly wrong to have $sign call clearsign -- sign/asksign results
> are supposed to be persistent across a single user interaction (%i/%o --
> see suprv1/meval*). This makes sense because the user has no way of
> knowing what internal/local scope they might be in.
>
> If a more local scope is wanted for a sign/asksign result, it should be
> handled using the context mechanism. I suppose you could try to do it also
> using unwind-protect etc., but that is tricky to get right. For example, I
> see that compar/asksign-p-or-n has a bug where if it is previously assumed
> that not equal(x,0), then (asksign-p-or-n x) will *remove* that
> preexisting assumption.
>
> I suppose there may be cases where the caller really knows that the result
> should not be persistent, and could call sign-plus-cleanup, but that seems
> like a really bad idea in general.
>
> -s
>
>
>
> On Fri, Aug 30, 2013 at 12:52 PM, Robert Dodier <robert.dodier at gmail.com>wrote:
>
>> On 2013-08-30, Raymond Toy <toy.raymond at gmail.com> wrote:
>>
>> > 3137b946bed77dc4311e4266ed338cd2d46d299f is the first bad commit
>> > commit 3137b946bed77dc4311e4266ed338cd2d46d299f
>> > Author: robert_dodier <robert_dodier at users.sourceforge.net>
>> > Date: Thu Mar 21 16:03:43 2013 -0700
>> >
>> > Call CLEARSIGN from $SIGN to clean up facts introduced by sign
>> functions.
>> >
>> > All versions before this commit are fine; you only have to answer one
>> > question and the integral is evaluated correctly. All versions after
>> this
>> > version are bad; you have to answer several questions and the integral
>> > is not evaluated.
>>
>> Hrm. That change was made to counteract some other strange behavior --
>> 'sign' left some facts floating around after it was called. Without
>> looking at the integration code, my guess is that it is assuming the
>> sign fact persists for the duration of the integration. Should there be
>> separate sign-plus-cleanup and sign-with-no-cleanup functions? It hurts
>> my head a little bit but maybe so ....
>>
>> Thanks for looking into it --
>>
>> Robert Dodier
>>
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>
>