12:25 p.m.
Oana,
Your reasoning is correct. The only thing I would change in your
rule is that you don't need the predicate. Just do the comparison directly:
Drink($speciality : speciality == $drinkS, $price : price)
The only better way I can think of is using the "accumulate"
conditional element, but this is only available in trunk:
when
Likes($nameS : name, $drinkS : drinkSpeciality)
$total : Double() from accumulate ( Drink($speciality :
speciality == $drinkS, $price : price)
init(
double total = 0 )
action(
total += $price )
result(
new Double( total ) ) )
then
// do something with the $total
end
You can use a global variable instead of an Accumulator class, but
this would force you to set the global variable in your java code
(before you call fireAllRules()), what may not ideal for such
situations. Using an accumulator instance allows you to define a setup
rule whose consequence asserts the accumulator instance, keeping your
launching code not dependent from your rules.
[]s
Edson
nicolae oana wrote:
Dear all,
In my problem, I have to calculate the sum of "price" field from many
Drink facts. Here is the code I have:
when
Likes($nameS : name, $drinkS : drinkSpeciality)
Drink(speciality == $drinkS, $price : price)
then
//calculate something like: totalPrice+=$price
Inspired from what Edson said, I've defined an Accumulator class and I
solve the problem:
when
$a:Accumulator()
Likes($nameS : name, $drinkS : drinkSpeciality)
Drink($speciality : speciality ->($speciality == $drinkS),
$price : price)
then
$a.incrementDrinksPrice($price.intValue());
In this context, my questions are:
1) Is there another appropriate solution to calculate the sum of prices?
2) What is the use of global variables? (because I think I
missunderstood their meanings). Can I solve my problem using a global
variable like an accumulator, knowing that a global variable is acting
like a static variable?
Best regards,
Oana.
*/Edson Tirelli <tirelli(a)post.com>/* wrote:
Jeevan, sorry, I missed your e-mail in the limbo.
Just create a class or an attribute to be your accumulator...
For instance, if you create a "branchCounter" attribute in the Tree
object, you can do that:
rule "Count branches" salience 10
when
$t : Tree()
Branch( tree == $t )
then
$t.incrementBranchCounter();
modify( $t );
end
rule "Check branch count" salience 0
when
$t : Tree( branchCounter > 100 )
then
// do something
end
The only trick is the salience. The first rule must have a higher
salience in order to only fire the second rule after all branches are
counted.
Yes, in trunk you could do better with "accumulate" or "collect".
For
your case, "collect" would be simpler:
rule "Check branches"
when
$t : Tree()
$branches : ArrayList( size > 100 ) from collect( Branch( tree ==
$t ) )
then
// do something
end
[]s
Edson
Jeevan Tambuluri wrote:
> Hello all,
>
> I have been told that you could implement a helper class to
simulate
> "accumulate" command in drools. Could you please ealborate on
how to
> do this? Some code snippet to illustrate this would be very much
> appreciated.
>
> My problem is as follows.I have two types of facts - Tree and
Branch.
> Each Branch object has a reference to the Tree object it belongs
to. I
> want to write a rule: The number of branches in a tree must not
> exceed 100. I guess this would be easy to write with "accumulate"
> command, which is not yet available in 3.0.x.
>
> Thanks
>
> Jeevan
>
>------------------------------------------------------------------------
>
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>
--
Edson Tirelli
Software Engineer - JBoss Rules Core Developer
Office: +55 11 3124-6000
Mobile: +55 11 9218-4151
JBoss, a division of Red Hat @ www.jboss.com
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Software Engineer - JBoss Rules Core Developer
Office: +55 11 3124-6000
Mobile: +55 11 9218-4151
JBoss, a division of Red Hat @ www.jboss.com