[rules-users] no-loop usage question

[Bryan Hansen]

I think I follow you now. If I was a little smarter with my conditional
statements to NOT keep assigning YES to something that is already set to YES
then it would probably eliminate the loop. In other words if I added more
checks like the ==null that you pointed out, I could (although I am not sure
that they are bad) remove the no-loop settings. Right?

Thanks,

Bryan

On Mon, Nov 3, 2008 at 9:17 AM, Joe White <Joe.White at recondotech.com> wrote:

>  You need no-loop on the rules because of the call to "modify(s)" . Modify
> changes the  fact in working memory and the engine is automatically
> notified of the changes at the end of the modify block. After modify the
> same rule could hit again as the conditions are still true.
>
>
>
> The first rule doesn't need the no-loop it because of the check "recommendPurchase
> == null"
>
>
>
> Joe
>
>
>
> *From:* rules-users-bounces at lists.jboss.org [mailto:
> rules-users-bounces at lists.jboss.org] *On Behalf Of *Bryan Hansen
> *Sent:* Sunday, November 02, 2008 8:21 PM
> *To:* rules-users at lists.jboss.org
> *Subject:* [rules-users] no-loop usage question
>
>
>
> I have been reading through the documentation and trying some of the
> tutorials and have a question about the no-loop attribute.
>
> Not really relevant to the post, but I figured I would mention it, I have
> been following this post and updating it to use the current version of
> Drools. http://www.onjava.com/pub/a/onjava/2005/08/03/drools.html?page=7
>
> I have written my rules as such:
>
> package org.drools.examples
>
> import org.drools.examples.StockOffer;
>
> rule PriceBelow100
>     dialect "java"
>     when
>         s: StockOffer( stockPrice < 100 && recommendPurchase == null )
>     then
>         modify( s ) {
>             setRecommendPurchase(StockOffer.YES)
>         }
> end
>
> rule NegativeStockPrice
>     dialect "java"
>     no-loop true
>     when
>         s: StockOffer( stockPrice < 0 )
>     then
>         modify( s ) {
>             setRecommendPurchase(StockOffer.NO)
>         }
> end
>
> rule DontBuyXYZStock
>     dialect "java"
>     no-loop true
>     when
>         s: StockOffer(stockName == "XYZ" && stockPrice < 10 )
>     then
>         modify( s ) {
>             setRecommendPurchase(StockOffer.YES)
>         }
> end
>
> rule BuyXYZStock
>     dialect "java"
>     no-loop true
>     when
>         s: StockOffer(stockName == "XYZ" && stockPrice > 10 )
>     then
>         modify( s ) {
>             setRecommendPurchase(StockOffer.NO)
>         }
> end
>
>
>
> My question is, why do I have to put no-loop on every rule (except for the
> first). After the first time through the rules, it shouldn't be modifying to
> where the rules would fire it again. Am I doing something wrong with how my
> rules are written? My sample data is this:
>
> package org.drools.examples;
>
> import org.drools.examples.BusinessLayer;
> import org.drools.examples.StockOffer;
>
> import junit.framework.TestCase;
>
> /*
>  * JUnit test for the business rules in the
>  * application.
>  *
>  * This also acts a 'simulator' for the business
>  * rules - allowing us to specify the inputs,
>  * examine the outputs and see if they match our
>  * expectations before letting the code loose in
>  * the real world.
>  */
> public class BusinessRuleTest extends TestCase {
>     /**
>      * Tests the purchase of a stock
>      */
>     public void testStockBuy() throws Exception {
>
>         // Create a Stock with simulated values
>         StockOffer testOffer = new StockOffer();
>         testOffer.setStockName("MEGACORP");
>         testOffer.setStockPrice(22);
>         testOffer.setStockQuantity(1000);
>
>         // Run the rules on it
>         BusinessLayer.evaluateStockPurchase(testOffer);
>
>         // Is it what we expected?
>         assertTrue(testOffer.getRecommendPurchase() != null);
>
>         assertTrue("YES".equals(testOffer.getRecommendPurchase()));
>     }
>
>     /**
>      * Tests the purchase of a stock makes sure the system will not accept
>      * negative numbers.
>      */
>     public void testNegativeStockBuy() throws Exception {
>
>         // Create a Stock with our simulated values
>         StockOffer testOffer = new StockOffer();
>         testOffer.setStockName("MEGACORP");
>         testOffer.setStockPrice(-22);
>         testOffer.setStockQuantity(1000);
>
>         // Run the rules on it
>         BusinessLayer.evaluateStockPurchase(testOffer);
>
>         // Is it what we expected?
>         assertTrue("NO".equals(testOffer.getRecommendPurchase()));
>     }
>
>     /**
>      * Makes sure the system will buy stocks of XYZ corp only if it really
> cheap
>      */
>     public void testXYZStockBuy() throws Exception {
>
>         // Create a Stock with our simulated values
>         StockOffer testOfferLow = new StockOffer();
>         StockOffer testOfferHigh = new StockOffer();
>
>         testOfferLow.setStockName("XYZ");
>         testOfferLow.setStockPrice(9);
>         testOfferLow.setStockQuantity(1000);
>
>         testOfferHigh.setStockName("XYZ");
>         testOfferHigh.setStockPrice(11);
>         testOfferHigh.setStockQuantity(1000);
>
>         // Run the rules on it and test
>         BusinessLayer.evaluateStockPurchase(testOfferLow);
>         assertTrue("YES".equals(testOfferLow.getRecommendPurchase()));
>
>         BusinessLayer.evaluateStockPurchase(testOfferHigh);
>         assertTrue("NO".equals(testOfferHigh.getRecommendPurchase()));
>     }
> }
>
>
> I can post up all the code if this isn't enough to answer the question.
>
> Thanks!
>
> _______________________________________________
> rules-users mailing list
> rules-users at lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/rules-users
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.jboss.org/pipermail/rules-users/attachments/20081103/7e8f656e/attachment.html