[rules-users] Strategy for initializing objects

[Wolfgang Laun]

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<robotnic%2Bdrools at gmail.com>>
> wrote:
>
> > From: sonia <robotnic+drools at gmail.com <robotnic%2Bdrools 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<robotnic%2Bdrools 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
> >
>
>
>
>
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