Why not simply use something like this:-
rule "TaxCalc"
when
$i : Invoice($st : salesTax, $gst : gstRate, $sa : salesAmount,
$id : importDuty, $gr : govtRebate)
then
$i.setTotalTax(round($st + ($gst * $sa / 100) + $id - $gr, 2));
update($i);
end
What do you gain by checking whether the Total Tax is different from the
value of the calculation? I must be missing something from your
simplified example?!?
(I think, big disclaimer!!) you could achieve your requirement using
eval and a tax value function that uses a cache under the hood, much
like the following:-
rule "TaxCalc"
when
$i : Invoice($tt : totalTax, $st : salesTax, $gst : gstRate,
$sa : salesAmount, $id : importDuty, $gr : govtRebate)
eval(Invoice($tt != taxFunction($st, $gst, $sa, Sid, $gr))
then
$i.setTotalTax(taxFunction($st, $gst, $sa, Sid, $gr);
update($i);
end
Evals cannot be indexed so you take a performance hit.
With kind regards,
Mike
________________________________
From: rules-users-boun...@lists.jboss.org
[mailto:rules-users-boun...@lists.jboss.org] On Behalf Of Shabbir Dhari
Sent: 03 July 2009 01:24
To: rules-users@lists.jboss.org
Subject: [rules-users] Formula value assginment in LHS
Dear all
We are developing a financial business application that contains
hundreds of business rules for validations and calculations. In the
calculation rules we change the value of attribute if values past in the
request is incorrect e.g.
rule "TaxCalc"
when
$i : Invoice()
Invoice (totalTax != (round(salesTax + (gstRate *
salesAmount / 100) + importDuty - govtRebate, 2)))
then
i.setTotalTax(round(salesTax + (gstRate * salesAmount /
100) + importDuty - govtRebate, 2));
end
The above code works perfectly fine. Only problem is the perform
calculation twice. What I was looking if possible I can store calculated
tax in a variable and simply assign variable to attribute if rule
condiation fails. Some thing like:
rule "TaxCalc"
when
$i : Invoice()
Invoice (totalTax != calTax : (round(salesTax + (gstRate
* salesAmount / 100)+ importDuty - govtRebate, 2)))
then
i.setTotalTax(calTax);
end
But this does not work - shows system error at calculated value
assignment. Is there any work around?
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