Have you looked at eval()?

From: rules-users-bounces@lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On Behalf Of tom ska
Sent: 06 August 2010 10:49
To: rules-users@lists.jboss.org
Subject: [rules-users] Math calculations on attributes in WHEN section of rules.

Hello,
what I want to do, is to calculate on object's attributes in WHEN section of rule. Can I do it?

For example:

class CObj
{
              private int k;
              private int n;

              // setters and getters
}

Now what I want to do is:

rule "r1"
    when
        p : CObj ( k + n <= 1000)
    then
        System.out.println("We love Drools :)");
end

Why can't I construct conditions like in Java, or C++ (with calculations in conditions)? How can I achieve my goal?

Thx,
Tom.