Order of operations

2008/4/9 Joe White < Joe.Whiterecondotech.com">Joe.Whiterecondotech.com>:

I have a question regarding order of operations in the consequence of a rule when using the mvel dialect. When executed the Drl below provides Right =30.0 and Wrong =140.0. The only difference is the parens around the multiplying expressions, which shouldn't be necessary given order of operations. Is this a problem with the drools/mvel interaction or is it completely an issue with mvel?

 

Is the general expectation that all expressions must be completely scoped by parens when using mvel?

&nbsp;

package test;

dialect "mvel"

rule "test 11"

 &nbsp;  when

 

 &nbsp;  then

 &nbsp; &nbsp; &nbsp;  double rightVal=((10-5)*2) + (5*(8-4));

 &nbsp; &nbsp; &nbsp;  double wrongVal=(10-5)*2 + 5*(8-4);

 

 &nbsp; &nbsp;    System.out.println("Right ="+rightVal);

 &nbsp; &nbsp;    System.out.println("Wrong ="+wrongVal);

End

 

After execution:

Right =30.0

Wrong =140.0

 

 

Thank you for all of your help. We are using drools 4.0.4.

 

Joe

 

Also, I haven't figured out how it arrives at 140. The following format also produces 140, which seems a little more strange.

 &nbsp; &nbsp; &nbsp;  double wrongVal=10-5*2 + 5*8-4;

 

 

 

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2008/4/9 Joe White < Joe.Whiterecondotech.com">Joe.Whiterecondotech.com>:

Another bug that  I just came across while working on getting my parens to work involved not handling scoped numbers properly. Similar to the previous one, but different in that it ends the expression evaluation prematurely. See the drl and result below:

 

package test;

dialect "mvel"

rule "test 12"

 &nbsp;  when

 

 &nbsp;  then

 &nbsp; &nbsp; &nbsp;  double rightVal=(10 + 12);

 &nbsp; &nbsp; &nbsp;  double wrongVal=(10) + (12);

 &nbsp; &nbsp;    double wrongValTwo = ((10)+12)

 &nbsp; &nbsp;    System.out.println("Right "+rightVal);

 &nbsp; &nbsp;    System.out.println("Wrong "+wrongVal);

 &nbsp; &nbsp;  &nbsp;System.out.println("WrongTwo ";+wrongValTwo);

End

 

Results in:

Right 22.0

Wrong 10.0

WrongTwo 10.0

 

Thanks,

Joe

 

From: rules-users-bounceslists.jboss.org" target="_blank">rules-users-bounceslists.jboss.org [mailto: rules-users-bounceslists.jboss.org" target="_blank">rules-users-bounceslists.jboss.org] On Behalf Of Edson Tirelli
Sent: Wednesday, April 09, 2008 12:39 PM
To: Rules Users List
Subject: Re: [rules-users] Order of operations

 ;

 &nbsp; Hi Joe,

  ; It seems someone skipped the elementary math lessons at school... :(

&nbsp;  Will open a JIRA for that.

 &nbsp; []s
&nbsp;  Edson

2008/4/9 Joe White < Joe.Whiterecondotech.com" target="_blank">Joe.Whiterecondotech.com>:

I have a question regarding order of operations in the consequence of a rule when using the mvel dialect. When executed the Drl below provides Right =30.0 and Wrong =140.0. The only difference is the parens around the multiplying expressions, which shouldn9;t be necessary given order of operations. Is this a problem with the drools/mvel interaction or is it completely an issue with mvel?

 

Is the general expectation that all expressions must be completely scoped by parens when using mvel?

&nbsp;

package test;

dialect "mvel"

rule "test 11"

 &nbsp;  when

 

 &nbsp;  then

 &nbsp; &nbsp; &nbsp;  double rightVal=((10-5)*2) + (5*(8-4));

 &nbsp; &nbsp; &nbsp;  double wrongVal=(10-5)*2 + 5*(8-4);

 

 &nbsp; &nbsp;    System.out.println("Right ="+rightVal);

 &nbsp; &nbsp;    System.out.println("Wrong ="+wrongVal);

End

 

After execution:

Right =30.0

Wrong =140.0

 

 

Thank you for all of your help. We are using drools 4.0.4.

 

Joe

 

Also, I haven't figured out how it arrives at 140. The following format also produces 140, which seems a little more strange.

 &nbsp; &nbsp; &nbsp;  double wrongVal=10-5*2 + 5*8-4;

 

 

 

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--
Edson Tirelli
JBoss Drools Core Development
Office: +55 11 3529-6000
Mobile: +55 11 9287-5646
JBoss, a division of Red Hat www.jboss.com

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