[rules-users] Strategy for initializing objects

[sonia]

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
>> > >
>> > >
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>> > > 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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-- 
robosonia