[rules-dev] modify (expr) catch 22

[Michael Anstis]

Wouldn't it be great(?) and an optimisation that with "true modify" (i.e. no
longer a remove and insert) that we could only re-evaluate rules that
contained a pattern on a constraint affected by the update?

So,

rule "MyRule"
  when
    $p : Person(name = "Yoda")
  then
    modify ($p) {
      setAge(300);
    }
end

would not cause "MyRule" to re-evaluate as there's enough information
present to ascertain that the modify does not alter the match.

Tell me Wolfgang, why this is such a bad idea - I just know you'll have a
good explanation :)

Cheers,

Mike

On 8 April 2011 13:00, Esteban Aliverti <esteban.aliverti at gmail.com> wrote:

> Yes, It creates the exact same infinite loop that this code does:
>
> rule "MyRule"
>   when
>     $p : Person(name = "Yoda")
>   then
>     $p.setAge(300);
>     update($p);
> end
>
> As far as I know, the results are the same. The modify() is a more compact
> way to do a lot of set() invocations and an update(). Maybe there are also
> some other advantages of using modify(), like optimization for example.
>
> Best Regards,
>
> XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
>
> Esteban Aliverti
> - Developer @ http://www.plugtree.com
> - Blog @ http://ilesteban.wordpress.com
>
>
>
> On Fri, Apr 8, 2011 at 8:39 AM, Geoffrey De Smet <ge0ffrey.spam at gmail.com>wrote:
>
>> Related to the modify expression,
>> I 've always wondered about this code:
>>
>> rule "MyRule"
>>   when
>>     $p : Person(name = "Yoda")
>>   then
>>     modify ($p) {
>>       setAge(300)
>>     }
>> end
>>
>> Doesn't this create an infinite loop? (In my experience it does or at
>> least it takes a lot longer)
>> Because the modify ($p) schedules any rule using a Person back on the
>> agenda to be re-evaluated,
>> so also that rule, which is evaluated and executed again, modifying $p
>> again, ... hence the infinite loop?
>>
>> --
>> With kind regards,
>> Geoffrey De Smet
>>
>>
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>> rules-dev at lists.jboss.org
>> https://lists.jboss.org/mailman/listinfo/rules-dev
>>
>
>
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