[rules-users] How to check for a variable number of "conditions" in a rule?

[Ron Kneusel]

Greetings!

I want to create a rule that checks a fact which contains an array to see if n or more of the elements of that array have a specific value.  The number of elements to check will vary from invocation to invocation of the rules engine and will likely be added as a global.

I can do this by using a helper function.  Say, for example, I have:

rule "fire_when_testFlags_true"
    when
        eval(testFlags(flags, limit.intValue()));
    then
        System.out.println("Yup, " + limit + " or more flags are true!");
end

Where flags and limit are both globals.  Then I can define testFlags as:

function boolean testFlags(Flags flags, int threshold) {
    int count = 0;

    for(int i=0; i < flags.getSize(); i++) {
        if (flags.getValue(i)) {
            count++;
            if (count>= threshold) {
                return true;
            }
        }
    }   
    return false;
}

This works but violates the warning not to use a global that isn't immutable in the LHS of a rule.  Does anyone have an idea about how to implement a rule that in effect has an arbitrary number of conditions to be tested?

Ron

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