[rules-users] Unexpected variable binding behavior and conditional logic

[Wolfgang Laun]

You are using 5.2.0?

I don't think that the *greatly simplified* version of your problem fails
the way you described.

However: https://issues.jboss.org/browse/JBRULES-3111 describes a very
similar issue, a severe regression from 5.1.1.

-W

On 19 July 2011 20:59, ChrisG <cgibble at excite.com> wrote:

> Apologies if this has been addressed elsewhere: I couldn't find anything
> quite like my issue.
>
> My (greatly simplified and completely made-up) example:
>
> Let's say I have this java class:
>
> public class BaseballPitcher
> {
>     public String getName();
>     public boolean isRightHanded();
>     public boolean isKnuckleBaller();
> }
>
> Multiple instances of this class are created with a variety of combinations
> for the name and two boolean parameters.
> Now I have a rule:
>
> rule "Match pitchers: righties or knuckle-ballers"
> when
>    $kbPitcher1 : BaseballPitcher($name: name, $righty: rightHanded == true
> ||
>           $knuckleballer: knuckleBaller == true)
>    $kbPitcher2:  BaseballPitcher(name != $name, rightHanded == $righty,
> knuckleBaller == $knuckleballer)
> then
>    // Do something with these two pitchers $kbPitcher1 and $kbPitcher2
> end
>
> I am getting the curious result that this rule fires its conclusion when
> $kbPitcher1 is in fact NEITHER right-handed nor a knuckle-baller (i.e.
> rightHanded == false && knuckleBaller == false).
>
> I've worked around this by changing the first condition in either of the
> following two ways:
>     *// eval() the condition*
>    $kbPitcher1 : BaseballPitcher($name: name, $righty: rightHanded,
> $knuckleballer: knuckleBaller,
>          *eval(isRightHanded() == true || isKnuckleBaller() == true)*)
> ...or....
>     *// bind the variables before checking values*
>    $kbPitcher1 : BaseballPitcher($name: name, $righty: rightHanded,
> $knuckleballer: knuckleBaller,
>          *rightHanded == true || knuckleBaller == true*)
>
> Does this make sense?  Both are easy workarounds, and I believe the second
> option (i.e. the one NOT using the eval) is the better solution from a
> performance perspective, allowing the engine to index the these facts
> rather
> than dynamically evaluate the condition every time.
>
> But I'm a little surprised the first approach didn't work.  Any ideas why
> not?
>
> --
> View this message in context:
> http://drools.46999.n3.nabble.com/Unexpected-variable-binding-behavior-and-conditional-logic-tp3183355p3183355.html
> Sent from the Drools: User forum mailing list archive at Nabble.com.
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