[rules-dev] [rules-users] MVEL parsing / keyword conflict

[Edson Tirelli]

   The DRL parser requires that the argument expression to a "from" CE be a
function call or a chained call to methods. The work around to that is to
call the MVEL "function" "return":

$items: LinkedList (size > 1) from collect ( Model ( ) from return(
object.getOriginal(null) in spatialIndex.query(...) ) )

   This way, the parser will passthrough whatever he finds inside the
return( ... ) to MVEL. Let us know if it works for you. I never tested that.

   []s
   Edson



2009/8/5 Simon Thum <simon.thum at gmx.de>

> Edson Tirelli wrote:
> >    Simon,
> >
> >    Can you show us what syntax are you trying?
> Sure, I was just speculating it's known or trivial.
>
> Works:
> $items: LinkedList (size > 1) from collect ( Model ( ) from
> spatialIndex.query(...) )
>
> Fails:
>
> $items: LinkedList (size > 1) from collect ( Model ( ) from
> >object.getOriginal(null) in spatialIndex.query(...)< )
>
> The angle brackets aren't typed, they just mark what's intended as mvel.
>
> >
> >    []s
> >    Edson
> >
> > 2009/8/5 Simon Thum <simon.thum at gmx.de>
> >
> >> Hi all,
> >>
> >> I've stumbled on some mvel integration issues in 5.0.1. I'm using drools
> >> to do, among others, spatial reasoning. At insertion time I maintain a
> >> specialized index, which can be queried later using [collect] from. This
> >> works fine in general.
> >>
> >> However, as soon as I use the mvel 2 projections a.k.a. 'in' keyword,
> >> hell breaks loose. 'in' is described here:
> >> http://mvel.codehaus.org/MVEL+2.0+Projections+and+Folds
> >>
> >> But I only seem to get syntax errors. If it is possible, to somehow
> >> escape keywords or explicitly pipe through the mvel part, please let me
> >> know!
> >>
> >> Needless to say, this feature would be great to have since my object
> >> model is mainly fixed and 'is' allows me to compensate that. Worse, I'd
> >> need to assert objects I don't want to assert to work around.
> >>
> >> I tried parenthesizing, only to discover that
> >> ... from valid_stmt
> >>
> >> is fine, but
> >>
> >> ... from (valid_stmt)
> >>
> >> won't work either. Error 101, reason unknown, but it doesn't even make
> >> it through the parser.
> >>
> >> I'd really appreciate to be given an idea why what I did went wrong.
> >> Googling around didn't get me too far.
> >>
> >> Cheers,
> >>
> >> Simon
> >> _______________________________________________
> >> rules-users mailing list
> >> rules-users at lists.jboss.org
> >> https://lists.jboss.org/mailman/listinfo/rules-users
> >>
> >
> >
> >
> >
> > ------------------------------------------------------------------------
> >
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>
>


-- 
 Edson Tirelli
 JBoss Drools Core Development
 JBoss by Red Hat @ www.jboss.com
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