Re: JESS: Strange behaviour of defadvice

Yes, a function can have only one advice. This wasn't originally the  
case, but experience showed that allowing multiple advice per function  
caused problems -- it was too easy to create infinite loops, for  
example.

You can solve your problem with a before-advice which unbinds the  
variables, calls bsave explicitly, rebinds the variables, and then  
returns. If you check the documentation, it explains that explicitly  
returning from a before-advice will result in the adviced function not  
being called automatically.


On Oct 7, 2010, at 8:44 AM, Gaëtan Pruvost wrote:

> Hi everybody,
>
> I have a problem with defadvice's behavior. It looks like you can't  
> add both a "before" and an "after" advice to the same function.
> Here is an example that demonstrates it
>
> (deffunction f ()
>     (printout t "during f" crlf))
>
> (defadvice before f (printout t "before f" crlf))
> (defadvice after f (printout t "after f" crlf))
>
> (f)
>
>
> It prints:
> Jess> (batch "test.clp")
> during f
> after f
> Jess>
>
> Looks like the after overwrote the before one and there is no way to  
> define both at the same time...
> I'm new to Jess so I hope this question is not stupid but i looked  
> in documentation and in the old mailling-list messages and found no  
> explaination for it. Is it the intended behaviour (in which case it  
> would be good to precise it in the doc) or a bug? I'm using the last  
> Jess71p2.
>
> I needed this to unbind global variables before a bsave and rebind  
> after the bsave (this variable refers to a java Logger which is not  
> serializable). I've found another solution wihtout using defadvice  
> but I find the defadvice more elegant.
>
>
> Best regards
> -- 
> ***********************************
> Gaëtan PRUVOST
>
> LIMSI-CNRS BP 133
> 91403 Orsay Cedex France
> Tel:+33 1 69858110
>
> http://www.limsi.fr/Individu/pruvost/
> ***********************************
> <gaetan_pruvost.vcf>

---------------------------------------------------------
Ernest Friedman-Hill
Informatics & Decision Sciences, Sandia National Laboratories
PO Box 969, MS 9012, Livermore, CA 94550
http://www.jessrules.com








--------------------------------------------------------------------
To unsubscribe, send the words 'unsubscribe jess-users [email protected]'
in the BODY of a message to [email protected], NOT to the list
(use your own address!) List problems? Notify [email protected].
--------------------------------------------------------------------