Well, I think the best thing to do is for you to upgrade to the
newest version of Jess and see if your problem goes away. I dug out an
archive of the final version of 4.1 (which went out with a
version-string reading 4.1b6) and tried your rule - it works OK for me
with both integral and floating point negative numbers:
c:/temp/Jess41> java jess.Main
Jess, the Java Expert System Shell
Copyright (C) 1998 E.J. Friedman Hill and the Sandia Corporation
Jess Version 4.1b6 8/20/98
Jess> (defrule set_abs
(number ?num&:(< ?num 0))
=>
(assert (abs_num (abs ?num)))
)
TRUE
Jess> (assert (number -1))
<Fact-0>
Jess> (run)
TRUE
Jess> (facts)
f-0 (number -1)
f-1 (abs_num 1)
For a total of 2 facts.
TRUE
Jess> (assert (number -1.0))
<Fact-2>
Jess> (run)
TRUE
Jess> (facts)
f-0 (number -1)
f-1 (abs_num 1)
f-2 (number -1.0)
f-3 (abs_num 1.0)
For a total of 4 facts.
TRUE
I think Christo Andonyadis wrote:
>
> Where ?b is a negative integer,
> the error I get on the (abs ?b) call is:
> Rete Exception in routine Value::Value while executing defrule
> set_abs_et.
> Message: not a float type: type = 0 at line 0: ( run ) .
>
> the error I get on the (- ?a ?b) is:
> Rete Exception in routine Value::Value while executing defrule
> time_between.
> Message: not a float type: type = 4 at line 0: ( run ) .
>
> I was hoping I had the syntax wrong.
> There is no problem using the "+" operator with negative numbers,
> only the "-" and apparently the abs function.
> The fact that (+ ?a ?b) where ?b is negative works but that (- ?a ?b)
> does not
> made me think that it was a bug in Jess.
> If I don't use varaibles the minus works i.e. (- 10 -5) gives 15.
>
> Thanks
> Christo
>
> Dr. Ernest J. Friedman-Hill wrote:
> >
> > I think Christo Andonyadis wrote:
> > >
> > > I'm using Jess 4.1.
> > > I get an error when trying to use the "-" operator with negative
> > > numbers.
> > > Is this a bug?
> >
> > Hard to say. WHat error do you get?
> >
> > >
> > > To work around this problem, I am trying to use the abs function to
> > > convert the negative number to a positive.
> > >
> > > What is wrong with this rule?
> > > (defrule set_abs
> > > (number ?num&:(< ?num 0))
> > > =>
> > > (assert (abs_num (abs ?num)))
> > > )
> >
> > I don't know. Looks fine to me. Does it cause a problem?
> >
> > Note that some JVMs have faulty versions of the stream tokenization
> > classes that older versions of Jess used to use (4.1 counts as older,
> > I think.) These faults could cause problems in parsing negative
> > numbers and the minus operator. Later versions of Jess work around
> > these problems by not using these classes. You could try upgrading
> > your JVM if it's an old one.
---------------------------------------------------------
Ernest Friedman-Hill
Distributed Systems Research Phone: (925) 294-2154
Sandia National Labs FAX: (925) 294-2234
Org. 8920, MS 9214 [EMAIL PROTECTED]
PO Box 969 http://herzberg.ca.sandia.gov
Livermore, CA 94550
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