[rules-users] Strategy for initializing objects

[Greg Barton]

Here's the drools fibonacci example, which is similar to what you want. (Initializing like objects based on ones "earlier" in a sequence.)

http://anonsvn.jboss.org/repos/labs/labs/jbossrules/trunk/drools-examples/drools-examples-drl/src/main/rules/org/drools/examples/Fibonacci.drl

http://anonsvn.jboss.org/repos/labs/labs/jbossrules/trunk/drools-examples/drools-examples-drl/src/main/java/org/drools/examples/FibonacciExample.java

--- On Sat, 8/8/09, Greg Barton <greg_barton at yahoo.com> wrote:

> From: Greg Barton <greg_barton at yahoo.com>
> Subject: Re: [rules-users] Strategy for initializing objects
> To: "Rules Users List" <rules-users at lists.jboss.org>
> Date: Saturday, August 8, 2009, 12:27 PM
> 
> Yes, unless you want the rules to react to the object in
> which you're accumulating the value.  Globals should
> not be used in rule conditions if they're mutable. (The rete
> network cannot be informed when they change.)
> 
> --- On Sat, 8/8/09, sonia <robotnic+drools at gmail.com>
> wrote:
> 
> > From: sonia <robotnic+drools at gmail.com>
> > Subject: Re: [rules-users] Strategy for initializing
> objects
> > To: "Rules Users List" <rules-users at lists.jboss.org>
> > Date: Saturday, August 8, 2009, 12:16 PM
> > Thank you.
> > 
> > Accumulating increasingly on every step seems better
> then
> > doing
> > 'accumulate' on all objects, all the time.
> > Logically, it is the same as what I wanted - to
> accumulate
> > the total
> > size somewhere. Implementation-wise, the difference is
> the
> > additional
> > fact object for accumulation.
> > 
> > Should I avoid using static or any non-fact external
> data
> > as part of
> > my calculations?
> > Isnt it just like using globals?
> > 
> > 2009/8/8 Wolfgang Laun <wolfgang.laun at gmail.com>:
> > > As an alternative, consider asserting a single
> Fact
> > Shelf with field x
> > > initially 0. Then you could do
> > >
> > > rule "Another box on the shelf"
> > > when
> > >     b: Box( x == -1, $size : size )
> > >     s: Shelf( $x : x )
> > > then
> > >     b.setX( $x ); update( b );
> > >     s.setX( $x + $size ); update( s );
> > > end
> > >
> > > -W
> > >
> > >
> > > 2009/8/8 Greg Barton <greg_barton at yahoo.com>
> > >>
> > >> You answer your own question.  Use
> accumulate:
> > >>
> > >> rule "Hello World"
> > >>        when
> > >>                b : Box( x == -1 )
> > >>                newX : Integer() from
> > accumulate( box: Box( x != -1 ),
> > >>                              
>  
> >  init( int i = 0; ),
> > >>                              
>  
> >  action( i += box.size; ),
> > >>                              
>  
> >  reverse( i -= box.size; ),
> > >>                              
>  
> >  result( i ) )
> > >>        then
> > >>              
>  System.out.println("Sum: "
> > + newX);
> > >>                b.setX(newX);
> > >>              
>  System.out.println(b);
> > >>                update(b);
> > >> end
> > >>
> > >> See attached project.
> > >>
> > >> --- On Sat, 8/8/09, sonia <robotnic+drools at gmail.com>
> > wrote:
> > >>
> > >> > From: sonia <robotnic+drools at gmail.com>
> > >> > Subject: Re: [rules-users] Strategy for
> > initializing objects
> > >> > To: "Rules Users List" <rules-users at lists.jboss.org>
> > >> > Date: Saturday, August 8, 2009, 2:36 AM
> > >> > In general: I want to set a property
> > >> > in the Box objects, depending on
> > >> > all previously set objects..
> > >> >
> > >> > My goal is to place the boxes one after
> > another, for this I
> > >> > keep a
> > >> > variable in Box object.
> > >> > It seems like the easiest way to
> accumulate
> > the sizes of
> > >> > boxes that
> > >> > are already placed.
> > >> >
> > >> > In the 'then' clause, I set the box
> location,
> > and update
> > >> > the X by
> > >> > adding the size of the currently placed
> box.
> > >> >
> > >> > 2009/8/8 Wolfgang Laun <wolfgang.laun at gmail.com>:
> > >> > > Your goal and the presented code
> aren't
> > clear to me.
> > >> > The consequence (after
> > >> > > then) contains calls to
> static/class
> > methods
> > >> > (Box.setX()) which isn't going
> > >> > > to change anything in your fact
> object.
> > The call
> > >> > b.setX() might change your
> > >> > > object, but this depends on what
> the
> > class method
> > >> > Box.getX() returns.
> > >> > >
> > >> > > Assuming Drools 5, a typical
> consequence
> > would look
> > >> > like
> > >> > >    b: Box(...)
> > >> > > then
> > >> > >    modify( b ){
> > >> > >       setX( ... )
> > >> > >    }
> > >> > > end
> > >> > >
> > >> > > -W
> > >> > >
> > >> > > On Sat, Aug 8, 2009 at 1:48 AM,
> sonia
> > <robotnic+drools at gmail.com>
> > >> > wrote:
> > >> > >>
> > >> > >> Hello
> > >> > >>
> > >> > >> I want to achieve this:
> > >> > >> box1.setX(0)
> > >> > >> box2.setX(box1.size());
> > >> > >> box2.setX(box1.size +
> box2.size)
> > >> > >> ...
> > >> > >>
> > >> > >> I want to do it with rules,
> and
> > would like to know
> > >> > what's the best
> > >> > >> method of initializing (or any
> other
> > operation
> > >> > with varying data) a
> > >> > >> group of objects
> > >> > >>
> > >> > >> rule "init box"
> > >> > >>  when
> > >> > >>   b : Box( x == -1)
> > >> > >>  then
> > >> > >>   b.setX(Box.getX());
> > >> > >>   Box.setX( Box.getX() +
> b.size);
> > >> > >> end
> > >> > >>
> > >> > >> This does not work.
> > >> > >> A single box object is matched
> > several times
> > >> > instead of different box
> > >> > >> objects.
> > >> > >> What is happening? how come a
> single
> > box object is
> > >> > matched several
> > >> > >> times? Why doesnt drools
> choose
> > other instances of
> > >> > box?
> > >> > >>
> > >> > >> What do I need to do to
> initialize
> > all boxes, once
> > >> > for every box?
> > >> > >>
> > >> > >> Thank you.
> > >> > >>
> > >> > >> --
> > >> > >> robosonia
> > >> > >>
> > _______________________________________________
> > >> > >> rules-users mailing list
> > >> > >> rules-users at lists.jboss.org
> > >> > >> https://lists.jboss.org/mailman/listinfo/rules-users
> > >> > >
> > >> > >
> > >> > >
> > _______________________________________________
> > >> > > rules-users mailing list
> > >> > > rules-users at lists.jboss.org
> > >> > > https://lists.jboss.org/mailman/listinfo/rules-users
> > >> > >
> > >> > >
> > >> >
> > >> >
> > >> >
> > >> > --
> > >> > robosonia
> > >> >
> > >> >
> > _______________________________________________
> > >> > rules-users mailing list
> > >> > rules-users at lists.jboss.org
> > >> > https://lists.jboss.org/mailman/listinfo/rules-users
> > >> >
> > >>
> > >>
> > >>
> > >>
> _______________________________________________
> > >> rules-users mailing list
> > >> rules-users at lists.jboss.org
> > >> https://lists.jboss.org/mailman/listinfo/rules-users
> > >>
> > >
> > >
> > > _______________________________________________
> > > rules-users mailing list
> > > rules-users at lists.jboss.org
> > > https://lists.jboss.org/mailman/listinfo/rules-users
> > >
> > >
> > 
> > 
> > 
> > -- 
> > robosonia
> > 
> > _______________________________________________
> > rules-users mailing list
> > rules-users at lists.jboss.org
> > https://lists.jboss.org/mailman/listinfo/rules-users
> > 
> 
> 
>       
> 
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