[rules-users] how to return additional information from method in'eval'

[Anstis, Michael (M.)]

I would have thought using some rule like this would solve your
problems?

Rule "identify non-overlapping intervals"
When
	$i: Interval()
	not exists Interval( ( this.intersects($i) ) )
Then
	//Add $i to database
End

Rule "identify overlapping intervals"
When
	$i: Interval()
	$ii: Interval( ( this.intersects($i) ) )
Then
	//$i intersects $ii
End

"This" is only available in v4, but I'm confident these rules can be
written in v3 syntax too.

Perhaps I have misunderstood your requirement.

With kind regards,

Mike
 

-----Original Message-----
From: rules-users-bounces at lists.jboss.org
[mailto:rules-users-bounces at lists.jboss.org] On Behalf Of Aeternitas
Sent: 26 June 2007 16:14
To: rules-users at lists.jboss.org
Subject: [rules-users] how to return additional information from method
in'eval'


Hello.

I have the following problem:
Let's imagine we have type like this - 
public class Interval{
  private long start;
  private long end;
  private int usage;
 ...
}

Now I need to insert in DB new Interval, but before doing it I have to
check, whether DB doesn't have any interval, which intersects new one
and
satisfies some rules (e.g. rules for summ of usage...). I use eval for
it -
I have method, which can check it using DB services etc. But... eval can
return only boolean... I want to know also why I can't insert this
interval
(e.g. which intervals prevent to do it). For me it will be comfortable
to do
something like this:

when
...
  # $intervals - collection of intervals, which intersects new interval
   $intervals : eval(newInterval)
  #<check whether size of intervals is great than 0>
then
  # We can insert such interval and using global variable we inform
about
it. 'error' it is collection of 
  # mistakes
  error.add("new interval can't be inserted because of " + <some
information
from $intervals> );

But it will not work (or maybe new engine, version 4, will allow such
'eval'
using ?). Could you advice anything?

(Method, which I use in eval have no access to the working memory, so I
can't use global variables. Also I don't want to fire such method again
in
"then" section to know "why I can't insert new interval")...

I hope I have described my problem clearly. Thanks in advance
Maxym
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