On 3/16/07, Tom Gonzalez <tomgon@nortel.com> wrote:

We handle it as it can't be anything else but null cause null is returned when an access fails or some error occurs. This keeps it from falling into a valid evaluation and possibly a subtle bug going uncaught.

Tom G

From: rules-dev-bounces@lists.jboss.org [mailto:rules-dev-bounces@lists.jboss.org] On Behalf Of Mark Proctor
Sent: Thursday, March 15, 2007 12:42 PM

To: Rules Dev List
Subject: Re: [rules-dev] need advice re null handling
Its not about giving it up, its how we handle when those fields are null, do we treat it like a primitive and assume its 0, or do we say it can't be equal to anything else but null.

In the following example neither y or z is defined, thus y is null and z is 0;

int x = 0;
Integer y;
in z;
x == y // is false;
x == z // is true
y == null // is true

Mark

Tom Gonzalez wrote:

The flexibility provided by an Object is very valuable. We use Integer and String objects all over the place today in our facts with drools. I would hate to give it up.

Tom G

From: rules-dev-bounces@lists.jboss.org [mailto:rules-dev-bounces@lists.jboss.org] On Behalf Of Mark Proctor
Sent: Thursday, March 15, 2007 6:29 AM
To: Rules Dev List
Subject: Re: [rules-dev] need advice re null handling

if bar is an integer it will be 0, if its an Integer it will be null. The Q is do we make Integer work like the primitive, or do we make it work like an Object.

Mark
Michael Neale wrote:
http://jira.jboss.com/jira/browse/JBRULES-627

OK, this much is clear:

Foo(field == null) can be true if field is null.

but, what about Foo(field > 3), and field is null? should that be false? what about Foo(field != 3) - should that be true?

in SQL, null will always result in a false condition, unless you explicitly use null.

Thoughts?

Michael.
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