4:56 p.m.
Hi everyone!
I'm relatively new to Drools and rule languages.
I'm wondering if it is possible to access the predecessor and successor in a
match using from operator on an (Array)List. I have something like this
(simplified):
...
$segment : Segment( countries contains Country.Switzerland && ... ) from
$journey.segmentList
$preSegment : Segment ( indexOf(this) == indexOf($segment) - 1,
countries not contains Country.Switzerland && ...
) from $journey.segmentList
I need something like indexOf() for the exact predecessor of the matched
segment.
If the matched business object was an element of a double linked list it
would be easy. Unfortunately I don't have the luxury to change the business
object into knowing it's predecessor or successor. I have to prove that we
could write our java coded business rules in Drools rule language without
changing the business object model.
Thanks in advance,
Chris
--
View this message in context:
http://www.nabble.com/Newbie-question-on-accessing-predecessor-and-succes...
Sent from the drools - user mailing list archive at Nabble.com.
5:31 p.m.
You can't do $journey.segmentList.indexOf(this) and
$journey.segmentList.indexOf($segment), even in an eval?
--- On Mon, 11/3/08, CSchr <christian.schrinner(a)sbb.ch> wrote:
From: CSchr <christian.schrinner(a)sbb.ch>
Subject: [rules-users] Newbie question on accessing predecessor and successor in a list
To: rules-users(a)lists.jboss.org
Date: Monday, November 3, 2008, 9:56 AM
Hi everyone!
I'm relatively new to Drools and rule languages.
I'm wondering if it is possible to access the
predecessor and successor in a
match using from operator on an (Array)List. I have
something like this
(simplified):
...
$segment : Segment( countries contains Country.Switzerland
&& ... ) from
$journey.segmentList
$preSegment : Segment ( indexOf(this) == indexOf($segment)
- 1,
countries not contains Country.Switzerland
&& ...
) from $journey.segmentList
I need something like indexOf() for the exact predecessor
of the matched
segment.
If the matched business object was an element of a double
linked list it
would be easy. Unfortunately I don't have the luxury to
change the business
object into knowing it's predecessor or successor. I
have to prove that we
could write our java coded business rules in Drools rule
language without
changing the business object model.
Thanks in advance,
Chris
--
View this message in context:
http://www.nabble.com/Newbie-question-on-accessing-predecessor-and-succes...
Sent from the drools - user mailing list archive at
Nabble.com.
_______________________________________________
rules-users mailing list
rules-users(a)lists.jboss.org
https://lists.jboss.org/mailman/listinfo/rules-users
8:45 a.m.
Thanks Greg for your fast reply. Unfortunately I do not get this to work:
$preSegment : Segment (
$journey.segmentList.indexOf(this) ==
($journey.segmentList.indexOf($segment) - 1),
countries not contains Country.Switzerland && ...
) from $journey.segmentList
Compiler throws:
[36,48]: unknown:36:48 Unexpected token 'this'[36,98]: unknown:36:98
Unexpected token '$segment'
Is it possible to use eval() inside Segment ()?
With eval the compiler throws something like this:
$journey.segmentList cannot be resolved to a type
Cannot use this in a static context
I don't know how matching works in drools, but wouldn't this also be very
expensive? As for every match of Segment ( ) the segmentList has to be
iterated two times. These lists can get very long. A cheap approach would be
if the from statement would "know" the index of the Segment () matched. I
was hoping this would be possible.
Regards,
Chris
Greg Barton wrote:
You can't do $journey.segmentList.indexOf(this) and
$journey.segmentList.indexOf($segment), even in an eval?
--- On Mon, 11/3/08, CSchr <christian.schrinner(a)sbb.ch> wrote:
> From: CSchr <christian.schrinner(a)sbb.ch>
> Subject: [rules-users] Newbie question on accessing predecessor and
> successor in a list
> To: rules-users(a)lists.jboss.org
> Date: Monday, November 3, 2008, 9:56 AM
> Hi everyone!
>
> I'm relatively new to Drools and rule languages.
>
> I'm wondering if it is possible to access the
> predecessor and successor in a
> match using from operator on an (Array)List. I have
> something like this
> (simplified):
>
> ...
> $segment : Segment( countries contains Country.Switzerland
> && ... ) from
> $journey.segmentList
>
> $preSegment : Segment ( indexOf(this) == indexOf($segment)
> - 1,
> countries not contains Country.Switzerland
> && ...
> ) from $journey.segmentList
>
> I need something like indexOf() for the exact predecessor
> of the matched
> segment.
>
> If the matched business object was an element of a double
> linked list it
> would be easy. Unfortunately I don't have the luxury to
> change the business
> object into knowing it's predecessor or successor. I
> have to prove that we
> could write our java coded business rules in Drools rule
> language without
> changing the business object model.
>
> Thanks in advance,
>
> Chris
>
>
> --
> View this message in context:
>
http://www.nabble.com/Newbie-question-on-accessing-predecessor-and-succes...
> Sent from the drools - user mailing list archive at
> Nabble.com.
>
> _______________________________________________
> rules-users mailing list
> rules-users(a)lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/rules-users
_______________________________________________
rules-users mailing list
rules-users(a)lists.jboss.org
https://lists.jboss.org/mailman/listinfo/rules-users
--
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http://www.nabble.com/Newbie-question-on-accessing-predecessor-and-succes...
Sent from the drools - user mailing list archive at Nabble.com.
3:56 p.m.
Christian,
My guess is that there are better approaches to do what you want (i.e.,
write your business rules) without using specific indexes in a list, since
that is usually a sign of trying to use a imperative algorithm in a
declarative engine.
If you can share a mock of what your business rule is, maybe we can help
more.
Having said that, about your questions:
* You can use eval inside patterns. Just remember that eval() uses a code
block in the same dialect you are using to write your rules (default is
java). So, $journey.segmentList is probably not valid in java (since
segmentList is probably private attribute), but is valid in MVEL that
transparently call getSegmentList(). So, either change your expression to a
correct java expression or change the rule dialect to MVEL.
* DISCLAIMER: THIS IS REALLY BAD PRACTICE: if you really want to emulate
"imperative programming" for this rule, you need a control fact to keep
track of the index you are testing:
rule "Children: do not do this at home, unless your parents says it is ok"
when
$cf : ControlFact( $pos : position < $journey.segmentList.size )
$s : Segment( countries contains Country.Switzerland, ... ) from
$journey.segmentList[$pos]
$ps : Segment( countries not contains Country.Switzerland, ... ) from
$journey.segmentList[$pos-1]
then
// do something
// and also update control fact
modify( $cf ) { setPosition( $pos + 1 ) }
end
Initialize control fact with position number 1 and it should be fine, but I
did not tested the above rule.
[]s
Edson
2008/11/4 CSchr <christian.schrinner(a)sbb.ch>
Thanks Greg for your fast reply. Unfortunately I do not get this to work:
$preSegment : Segment (
$journey.segmentList.indexOf(this) ==
($journey.segmentList.indexOf($segment) - 1),
countries not contains Country.Switzerland && ...
) from $journey.segmentList
Compiler throws:
[36,48]: unknown:36:48 Unexpected token 'this'[36,98]: unknown:36:98
Unexpected token '$segment'
Is it possible to use eval() inside Segment ()?
With eval the compiler throws something like this:
$journey.segmentList cannot be resolved to a type
Cannot use this in a static context
I don't know how matching works in drools, but wouldn't this also be very
expensive? As for every match of Segment ( ) the segmentList has to be
iterated two times. These lists can get very long. A cheap approach would
be
if the from statement would "know" the index of the Segment () matched. I
was hoping this would be possible.
Regards,
Chris
Greg Barton wrote:
>
> You can't do $journey.segmentList.indexOf(this) and
> $journey.segmentList.indexOf($segment), even in an eval?
>
> --- On Mon, 11/3/08, CSchr <christian.schrinner(a)sbb.ch> wrote:
>
>> From: CSchr <christian.schrinner(a)sbb.ch>
>> Subject: [rules-users] Newbie question on accessing predecessor and
>> successor in a list
>> To: rules-users(a)lists.jboss.org
>> Date: Monday, November 3, 2008, 9:56 AM
>> Hi everyone!
>>
>> I'm relatively new to Drools and rule languages.
>>
>> I'm wondering if it is possible to access the
>> predecessor and successor in a
>> match using from operator on an (Array)List. I have
>> something like this
>> (simplified):
>>
>> ...
>> $segment : Segment( countries contains Country.Switzerland
>> && ... ) from
>> $journey.segmentList
>>
>> $preSegment : Segment ( indexOf(this) == indexOf($segment)
>> - 1,
>> countries not contains
Country.Switzerland
>> && ...
>> ) from $journey.segmentList
>>
>> I need something like indexOf() for the exact predecessor
>> of the matched
>> segment.
>>
>> If the matched business object was an element of a double
>> linked list it
>> would be easy. Unfortunately I don't have the luxury to
>> change the business
>> object into knowing it's predecessor or successor. I
>> have to prove that we
>> could write our java coded business rules in Drools rule
>> language without
>> changing the business object model.
>>
>> Thanks in advance,
>>
>> Chris
>>
>>
>> --
>> View this message in context:
>>
http://www.nabble.com/Newbie-question-on-accessing-predecessor-and-succes...
>> Sent from the drools - user mailing list archive at
>> Nabble.com.
>>
>> _______________________________________________
>> rules-users mailing list
>> rules-users(a)lists.jboss.org
>> https://lists.jboss.org/mailman/listinfo/rules-users
>
>
>
> _______________________________________________
> rules-users mailing list
> rules-users(a)lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/rules-users
>
>
--
View this message in context:
http://www.nabble.com/Newbie-question-on-accessing-predecessor-and-succes...
Sent from the drools - user mailing list archive at Nabble.com.
_______________________________________________
rules-users mailing list
rules-users(a)lists.jboss.org
https://lists.jboss.org/mailman/listinfo/rules-users
--
Edson Tirelli
JBoss Drools Core Development
JBoss, a division of Red Hat @ www.jboss.com
4:37 p.m.
I think you'd have to toss in ControlFact instances with positions from 1 to
journey.segmentList.size-1 for this to work. Otherwise the evaluation of the
journey.segmentList would halt on the first failure of the rule to match. Then the modify
block wouldn't be needed in the action.
Also, CSchr, you mentioned that the business model could not be altered. Does that mean
you can't use additional objects like control facts?
--- On Tue, 11/4/08, Edson Tirelli <tirelli(a)post.com> wrote:
From: Edson Tirelli <tirelli(a)post.com>
Subject: Re: [rules-users] Newbie question on accessing predecessor and successor in a
list
To: "Rules Users List" <rules-users(a)lists.jboss.org>
Date: Tuesday, November 4, 2008, 8:56 AM
Christian,
My guess is that there are better approaches to do what
you want (i.e.,
write your business rules) without using specific indexes
in a list, since
that is usually a sign of trying to use a imperative
algorithm in a
declarative engine.
If you can share a mock of what your business rule is,
maybe we can help
more.
Having said that, about your questions:
* You can use eval inside patterns. Just remember that
eval() uses a code
block in the same dialect you are using to write your rules
(default is
java). So, $journey.segmentList is probably not valid in
java (since
segmentList is probably private attribute), but is valid in
MVEL that
transparently call getSegmentList(). So, either change your
expression to a
correct java expression or change the rule dialect to MVEL.
* DISCLAIMER: THIS IS REALLY BAD PRACTICE: if you really
want to emulate
"imperative programming" for this rule, you need
a control fact to keep
track of the index you are testing:
rule "Children: do not do this at home, unless your
parents says it is ok"
when
$cf : ControlFact( $pos : position <
$journey.segmentList.size )
$s : Segment( countries contains Country.Switzerland,
... ) from
$journey.segmentList[$pos]
$ps : Segment( countries not contains
Country.Switzerland, ... ) from
$journey.segmentList[$pos-1]
then
// do something
// and also update control fact
modify( $cf ) { setPosition( $pos + 1 ) }
end
Initialize control fact with position number 1 and it
should be fine, but I
did not tested the above rule.
[]s
Edson
2008/11/4 CSchr <christian.schrinner(a)sbb.ch>
>
> Thanks Greg for your fast reply. Unfortunately I do
not get this to work:
>
> $preSegment : Segment (
>
$journey.segmentList.indexOf(this) ==
> ($journey.segmentList.indexOf($segment) - 1),
> countries not contains
Country.Switzerland && ...
> ) from $journey.segmentList
>
> Compiler throws:
>
> [36,48]: unknown:36:48 Unexpected token
'this'[36,98]: unknown:36:98
> Unexpected token '$segment'
>
> Is it possible to use eval() inside Segment ()?
>
> With eval the compiler throws something like this:
>
> $journey.segmentList cannot be resolved to a type
> Cannot use this in a static context
>
> I don't know how matching works in drools, but
wouldn't this also be very
> expensive? As for every match of Segment ( ) the
segmentList has to be
> iterated two times. These lists can get very long. A
cheap approach would
> be
> if the from statement would "know" the index
of the Segment () matched. I
> was hoping this would be possible.
>
>
> Regards,
>
> Chris
>
>
> Greg Barton wrote:
> >
> > You can't do
$journey.segmentList.indexOf(this) and
> > $journey.segmentList.indexOf($segment), even in
an eval?
> >
> > --- On Mon, 11/3/08, CSchr
<christian.schrinner(a)sbb.ch> wrote:
> >
> >> From: CSchr
<christian.schrinner(a)sbb.ch>
> >> Subject: [rules-users] Newbie question on
accessing predecessor and
> >> successor in a list
> >> To: rules-users(a)lists.jboss.org
> >> Date: Monday, November 3, 2008, 9:56 AM
> >> Hi everyone!
> >>
> >> I'm relatively new to Drools and rule
languages.
> >>
> >> I'm wondering if it is possible to access
the
> >> predecessor and successor in a
> >> match using from operator on an (Array)List.
I have
> >> something like this
> >> (simplified):
> >>
> >> ...
> >> $segment : Segment( countries contains
Country.Switzerland
> >> && ... ) from
> >> $journey.segmentList
> >>
> >> $preSegment : Segment ( indexOf(this) ==
indexOf($segment)
> >> - 1,
> >> countries not
contains
> Country.Switzerland
> >> && ...
> >> ) from $journey.segmentList
> >>
> >> I need something like indexOf() for the exact
predecessor
> >> of the matched
> >> segment.
> >>
> >> If the matched business object was an element
of a double
> >> linked list it
> >> would be easy. Unfortunately I don't have
the luxury to
> >> change the business
> >> object into knowing it's predecessor or
successor. I
> >> have to prove that we
> >> could write our java coded business rules in
Drools rule
> >> language without
> >> changing the business object model.
> >>
> >> Thanks in advance,
> >>
> >> Chris
> >>
> >>
> >> --
> >> View this message in context:
> >>
>
http://www.nabble.com/Newbie-question-on-accessing-predecessor-and-succes...
> >> Sent from the drools - user mailing list
archive at
> >> Nabble.com.
> >>
> >>
_______________________________________________
> >> rules-users mailing list
> >> rules-users(a)lists.jboss.org
> >>
https://lists.jboss.org/mailman/listinfo/rules-users
> >
> >
> >
> > _______________________________________________
> > rules-users mailing list
> > rules-users(a)lists.jboss.org
> >
https://lists.jboss.org/mailman/listinfo/rules-users
> >
> >
>
> --
> View this message in context:
>
http://www.nabble.com/Newbie-question-on-accessing-predecessor-and-succes...
> Sent from the drools - user mailing list archive at
Nabble.com.
>
> _______________________________________________
> rules-users mailing list
> rules-users(a)lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/rules-users
>
--
Edson Tirelli
JBoss Drools Core Development
JBoss, a division of Red Hat @ www.jboss.com
_______________________________________________
rules-users mailing list
rules-users(a)lists.jboss.org
https://lists.jboss.org/mailman/listinfo/rules-users
5:01 p.m.
Good point Greg, thanks!
Either that or move the actual update on the control fact to a rule with
lower salience.
[]s
Edson
2008/11/4 Greg Barton <greg_barton(a)yahoo.com>
I think you'd have to toss in ControlFact instances with
positions from 1
to journey.segmentList.size-1 for this to work. Otherwise the evaluation of
the journey.segmentList would halt on the first failure of the rule to
match. Then the modify block wouldn't be needed in the action.
Also, CSchr, you mentioned that the business model could not be altered.
Does that mean you can't use additional objects like control facts?
--- On Tue, 11/4/08, Edson Tirelli <tirelli(a)post.com> wrote:
> From: Edson Tirelli <tirelli(a)post.com>
> Subject: Re: [rules-users] Newbie question on accessing predecessor and
successor in a list
> To: "Rules Users List" <rules-users(a)lists.jboss.org>
> Date: Tuesday, November 4, 2008, 8:56 AM
> Christian,
>
> My guess is that there are better approaches to do what
> you want (i.e.,
> write your business rules) without using specific indexes
> in a list, since
> that is usually a sign of trying to use a imperative
> algorithm in a
> declarative engine.
> If you can share a mock of what your business rule is,
> maybe we can help
> more.
>
> Having said that, about your questions:
>
> * You can use eval inside patterns. Just remember that
> eval() uses a code
> block in the same dialect you are using to write your rules
> (default is
> java). So, $journey.segmentList is probably not valid in
> java (since
> segmentList is probably private attribute), but is valid in
> MVEL that
> transparently call getSegmentList(). So, either change your
> expression to a
> correct java expression or change the rule dialect to MVEL.
>
> * DISCLAIMER: THIS IS REALLY BAD PRACTICE: if you really
> want to emulate
> "imperative programming" for this rule, you need
> a control fact to keep
> track of the index you are testing:
>
> rule "Children: do not do this at home, unless your
> parents says it is ok"
> when
> $cf : ControlFact( $pos : position <
> $journey.segmentList.size )
> $s : Segment( countries contains Country.Switzerland,
> ... ) from
> $journey.segmentList[$pos]
> $ps : Segment( countries not contains
> Country.Switzerland, ... ) from
> $journey.segmentList[$pos-1]
> then
> // do something
> // and also update control fact
> modify( $cf ) { setPosition( $pos + 1 ) }
> end
>
> Initialize control fact with position number 1 and it
> should be fine, but I
> did not tested the above rule.
>
> []s
> Edson
>
>
> 2008/11/4 CSchr <christian.schrinner(a)sbb.ch>
>
> >
> > Thanks Greg for your fast reply. Unfortunately I do
> not get this to work:
> >
> > $preSegment : Segment (
> >
> $journey.segmentList.indexOf(this) ==
> > ($journey.segmentList.indexOf($segment) - 1),
> > countries not contains
> Country.Switzerland && ...
> > ) from $journey.segmentList
> >
> > Compiler throws:
> >
> > [36,48]: unknown:36:48 Unexpected token
> 'this'[36,98]: unknown:36:98
> > Unexpected token '$segment'
> >
> > Is it possible to use eval() inside Segment ()?
> >
> > With eval the compiler throws something like this:
> >
> > $journey.segmentList cannot be resolved to a type
> > Cannot use this in a static context
> >
> > I don't know how matching works in drools, but
> wouldn't this also be very
> > expensive? As for every match of Segment ( ) the
> segmentList has to be
> > iterated two times. These lists can get very long. A
> cheap approach would
> > be
> > if the from statement would "know" the index
> of the Segment () matched. I
> > was hoping this would be possible.
> >
> >
> > Regards,
> >
> > Chris
> >
> >
> > Greg Barton wrote:
> > >
> > > You can't do
> $journey.segmentList.indexOf(this) and
> > > $journey.segmentList.indexOf($segment), even in
> an eval?
> > >
> > > --- On Mon, 11/3/08, CSchr
> <christian.schrinner(a)sbb.ch> wrote:
> > >
> > >> From: CSchr
> <christian.schrinner(a)sbb.ch>
> > >> Subject: [rules-users] Newbie question on
> accessing predecessor and
> > >> successor in a list
> > >> To: rules-users(a)lists.jboss.org
> > >> Date: Monday, November 3, 2008, 9:56 AM
> > >> Hi everyone!
> > >>
> > >> I'm relatively new to Drools and rule
> languages.
> > >>
> > >> I'm wondering if it is possible to access
> the
> > >> predecessor and successor in a
> > >> match using from operator on an (Array)List.
> I have
> > >> something like this
> > >> (simplified):
> > >>
> > >> ...
> > >> $segment : Segment( countries contains
> Country.Switzerland
> > >> && ... ) from
> > >> $journey.segmentList
> > >>
> > >> $preSegment : Segment ( indexOf(this) ==
> indexOf($segment)
> > >> - 1,
> > >> countries not
> contains
> > Country.Switzerland
> > >> && ...
> > >> ) from $journey.segmentList
> > >>
> > >> I need something like indexOf() for the exact
> predecessor
> > >> of the matched
> > >> segment.
> > >>
> > >> If the matched business object was an element
> of a double
> > >> linked list it
> > >> would be easy. Unfortunately I don't have
> the luxury to
> > >> change the business
> > >> object into knowing it's predecessor or
> successor. I
> > >> have to prove that we
> > >> could write our java coded business rules in
> Drools rule
> > >> language without
> > >> changing the business object model.
> > >>
> > >> Thanks in advance,
> > >>
> > >> Chris
> > >>
> > >>
> > >> --
> > >> View this message in context:
> > >>
> >
>
http://www.nabble.com/Newbie-question-on-accessing-predecessor-and-succes...
> > >> Sent from the drools - user mailing list
> archive at
> > >> Nabble.com.
> > >>
> > >>
> _______________________________________________
> > >> rules-users mailing list
> > >> rules-users(a)lists.jboss.org
> > >>
> https://lists.jboss.org/mailman/listinfo/rules-users
> > >
> > >
> > >
> > > _______________________________________________
> > > rules-users mailing list
> > > rules-users(a)lists.jboss.org
> > >
> https://lists.jboss.org/mailman/listinfo/rules-users
> > >
> > >
> >
> > --
> > View this message in context:
> >
>
http://www.nabble.com/Newbie-question-on-accessing-predecessor-and-succes...
> > Sent from the drools - user mailing list archive at
> Nabble.com.
> >
> > _______________________________________________
> > rules-users mailing list
> > rules-users(a)lists.jboss.org
> > https://lists.jboss.org/mailman/listinfo/rules-users
> >
>
>
>
> --
> Edson Tirelli
> JBoss Drools Core Development
> JBoss, a division of Red Hat @ www.jboss.com
> _______________________________________________
> rules-users mailing list
> rules-users(a)lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/rules-users
_______________________________________________
rules-users mailing list
rules-users(a)lists.jboss.org
https://lists.jboss.org/mailman/listinfo/rules-users
--
Edson Tirelli
JBoss Drools Core Development
JBoss, a division of Red Hat @ www.jboss.com
5:58 p.m.
Yes that's correct. No way to change the model yet. But I think I could
introduce additional objects and could even "clone" the business objects
into more convenient objects just for rule evaluation. But this would be my
least prefered solution as it would introduce a layer of transformation and
a parallel (mirror) model that needs to be updated whenever the business
model changes in future releases.
Regards,
Chris
Greg Barton wrote:
I think you'd have to toss in ControlFact instances with positions from 1
to journey.segmentList.size-1 for this to work. Otherwise the evaluation
of the journey.segmentList would halt on the first failure of the rule to
match. Then the modify block wouldn't be needed in the action.
Also, CSchr, you mentioned that the business model could not be altered.
Does that mean you can't use additional objects like control facts?
--- On Tue, 11/4/08, Edson Tirelli <tirelli(a)post.com> wrote:
> From: Edson Tirelli <tirelli(a)post.com>
> Subject: Re: [rules-users] Newbie question on accessing predecessor and
> successor in a list
> To: "Rules Users List" <rules-users(a)lists.jboss.org>
> Date: Tuesday, November 4, 2008, 8:56 AM
> Christian,
>
> My guess is that there are better approaches to do what
> you want (i.e.,
> write your business rules) without using specific indexes
> in a list, since
> that is usually a sign of trying to use a imperative
> algorithm in a
> declarative engine.
> If you can share a mock of what your business rule is,
> maybe we can help
> more.
>
> Having said that, about your questions:
>
> * You can use eval inside patterns. Just remember that
> eval() uses a code
> block in the same dialect you are using to write your rules
> (default is
> java). So, $journey.segmentList is probably not valid in
> java (since
> segmentList is probably private attribute), but is valid in
> MVEL that
> transparently call getSegmentList(). So, either change your
> expression to a
> correct java expression or change the rule dialect to MVEL.
>
> * DISCLAIMER: THIS IS REALLY BAD PRACTICE: if you really
> want to emulate
> "imperative programming" for this rule, you need
> a control fact to keep
> track of the index you are testing:
>
> rule "Children: do not do this at home, unless your
> parents says it is ok"
> when
> $cf : ControlFact( $pos : position <
> $journey.segmentList.size )
> $s : Segment( countries contains Country.Switzerland,
> ... ) from
> $journey.segmentList[$pos]
> $ps : Segment( countries not contains
> Country.Switzerland, ... ) from
> $journey.segmentList[$pos-1]
> then
> // do something
> // and also update control fact
> modify( $cf ) { setPosition( $pos + 1 ) }
> end
>
> Initialize control fact with position number 1 and it
> should be fine, but I
> did not tested the above rule.
>
> []s
> Edson
>
>
> 2008/11/4 CSchr <christian.schrinner(a)sbb.ch>
>
> >
> > Thanks Greg for your fast reply. Unfortunately I do
> not get this to work:
> >
> > $preSegment : Segment (
> >
> $journey.segmentList.indexOf(this) ==
> > ($journey.segmentList.indexOf($segment) - 1),
> > countries not contains
> Country.Switzerland && ...
> > ) from $journey.segmentList
> >
> > Compiler throws:
> >
> > [36,48]: unknown:36:48 Unexpected token
> 'this'[36,98]: unknown:36:98
> > Unexpected token '$segment'
> >
> > Is it possible to use eval() inside Segment ()?
> >
> > With eval the compiler throws something like this:
> >
> > $journey.segmentList cannot be resolved to a type
> > Cannot use this in a static context
> >
> > I don't know how matching works in drools, but
> wouldn't this also be very
> > expensive? As for every match of Segment ( ) the
> segmentList has to be
> > iterated two times. These lists can get very long. A
> cheap approach would
> > be
> > if the from statement would "know" the index
> of the Segment () matched. I
> > was hoping this would be possible.
> >
> >
> > Regards,
> >
> > Chris
> >
> >
> > Greg Barton wrote:
> > >
> > > You can't do
> $journey.segmentList.indexOf(this) and
> > > $journey.segmentList.indexOf($segment), even in
> an eval?
> > >
> > > --- On Mon, 11/3/08, CSchr
> <christian.schrinner(a)sbb.ch> wrote:
> > >
> > >> From: CSchr
> <christian.schrinner(a)sbb.ch>
> > >> Subject: [rules-users] Newbie question on
> accessing predecessor and
> > >> successor in a list
> > >> To: rules-users(a)lists.jboss.org
> > >> Date: Monday, November 3, 2008, 9:56 AM
> > >> Hi everyone!
> > >>
> > >> I'm relatively new to Drools and rule
> languages.
> > >>
> > >> I'm wondering if it is possible to access
> the
> > >> predecessor and successor in a
> > >> match using from operator on an (Array)List.
> I have
> > >> something like this
> > >> (simplified):
> > >>
> > >> ...
> > >> $segment : Segment( countries contains
> Country.Switzerland
> > >> && ... ) from
> > >> $journey.segmentList
> > >>
> > >> $preSegment : Segment ( indexOf(this) ==
> indexOf($segment)
> > >> - 1,
> > >> countries not
> contains
> > Country.Switzerland
> > >> && ...
> > >> ) from $journey.segmentList
> > >>
> > >> I need something like indexOf() for the exact
> predecessor
> > >> of the matched
> > >> segment.
> > >>
> > >> If the matched business object was an element
> of a double
> > >> linked list it
> > >> would be easy. Unfortunately I don't have
> the luxury to
> > >> change the business
> > >> object into knowing it's predecessor or
> successor. I
> > >> have to prove that we
> > >> could write our java coded business rules in
> Drools rule
> > >> language without
> > >> changing the business object model.
> > >>
> > >> Thanks in advance,
> > >>
> > >> Chris
> > >>
> > >>
> > >> --
> > >> View this message in context:
> > >>
> >
>
http://www.nabble.com/Newbie-question-on-accessing-predecessor-and-succes...
> > >> Sent from the drools - user mailing list
> archive at
> > >> Nabble.com.
> > >>
> > >>
> _______________________________________________
> > >> rules-users mailing list
> > >> rules-users(a)lists.jboss.org
> > >>
> https://lists.jboss.org/mailman/listinfo/rules-users
> > >
> > >
> > >
> > > _______________________________________________
> > > rules-users mailing list
> > > rules-users(a)lists.jboss.org
> > >
> https://lists.jboss.org/mailman/listinfo/rules-users
> > >
> > >
> >
> > --
> > View this message in context:
> >
>
http://www.nabble.com/Newbie-question-on-accessing-predecessor-and-succes...
> > Sent from the drools - user mailing list archive at
> Nabble.com.
> >
> > _______________________________________________
> > rules-users mailing list
> > rules-users(a)lists.jboss.org
> > https://lists.jboss.org/mailman/listinfo/rules-users
> >
>
>
>
> --
> Edson Tirelli
> JBoss Drools Core Development
> JBoss, a division of Red Hat @ www.jboss.com
> _______________________________________________
> rules-users mailing list
> rules-users(a)lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/rules-users
_______________________________________________
rules-users mailing list
rules-users(a)lists.jboss.org
https://lists.jboss.org/mailman/listinfo/rules-users
--
View this message in context:
http://www.nabble.com/Newbie-question-on-accessing-predecessor-and-succes...
Sent from the drools - user mailing list archive at Nabble.com.
6:28 p.m.
Chris,
You wouldn't necessarily need to clone you business objects. If you create classes
that had them as attributes and injected your "new" classes into the rules
engine, you could accomplish both goals: no parallel model and classes that support the
needs of your rules.
Earnie!
________________________________
From: CSchr <christian.schrinner(a)sbb.ch>
To: rules-users(a)lists.jboss.org
Sent: Tuesday, November 4, 2008 11:58:22 AM
Subject: Re: [rules-users] Newbie question on accessing predecessor and successor in a
list
Yes that's correct. No way to change the model yet. But I think I could
introduce additional objects and could even "clone" the business objects
into more convenient objects just for rule evaluation. But this would be my
least prefered solution as it would introduce a layer of transformation and
a parallel (mirror) model that needs to be updated whenever the business
model changes in future releases.
Regards,
Chris
Greg Barton wrote:
I think you'd have to toss in ControlFact instances with positions from 1
to journey.segmentList.size-1 for this to work. Otherwise the evaluation
of the journey.segmentList would halt on the first failure of the rule to
match. Then the modify block wouldn't be needed in the action.
Also, CSchr, you mentioned that the business model could not be altered.
Does that mean you can't use additional objects like control facts?
--- On Tue, 11/4/08, Edson Tirelli <tirelli(a)post.com> wrote:
> From: Edson Tirelli <tirelli(a)post.com>
> Subject: Re: [rules-users] Newbie question on accessing predecessor and
> successor in a list
> To: "Rules Users List" <rules-users(a)lists.jboss.org>
> Date: Tuesday, November 4, 2008, 8:56 AM
> Christian,
>
> My guess is that there are better approaches to do what
> you want (i.e.,
> write your business rules) without using specific indexes
> in a list, since
> that is usually a sign of trying to use a imperative
> algorithm in a
> declarative engine.
> If you can share a mock of what your business rule is,
> maybe we can help
> more.
>
> Having said that, about your questions:
>
> * You can use eval inside patterns. Just remember that
> eval() uses a code
> block in the same dialect you are using to write your rules
> (default is
> java). So, $journey.segmentList is probably not valid in
> java (since
> segmentList is probably private attribute), but is valid in
> MVEL that
> transparently call getSegmentList(). So, either change your
> expression to a
> correct java expression or change the rule dialect to MVEL.
>
> * DISCLAIMER: THIS IS REALLY BAD PRACTICE: if you really
> want to emulate
> "imperative programming" for this rule, you need
> a control fact to keep
> track of the index you are testing:
>
> rule "Children: do not do this at home, unless your
> parents says it is ok"
> when
> $cf : ControlFact( $pos : position <
> $journey.segmentList.size )
> $s : Segment( countries contains Country.Switzerland,
> ... ) from
> $journey.segmentList[$pos]
> $ps : Segment( countries not contains
> Country.Switzerland, ... ) from
> $journey.segmentList[$pos-1]
> then
> // do something
> // and also update control fact
> modify( $cf ) { setPosition( $pos + 1 ) }
> end
>
> Initialize control fact with position number 1 and it
> should be fine, but I
> did not tested the above rule.
>
> []s
> Edson
>
>
> 2008/11/4 CSchr <christian.schrinner(a)sbb.ch>
>
> >
> > Thanks Greg for your fast reply. Unfortunately I do
> not get this to work:
> >
> > $preSegment : Segment (
> >
> $journey.segmentList.indexOf(this) ==
> > ($journey.segmentList.indexOf($segment) - 1),
> > countries not contains
> Country.Switzerland && ...
> > ) from $journey.segmentList
> >
> > Compiler throws:
> >
> > [36,48]: unknown:36:48 Unexpected token
> 'this'[36,98]: unknown:36:98
> > Unexpected token '$segment'
> >
> > Is it possible to use eval() inside Segment ()?
> >
> > With eval the compiler throws something like this:
> >
> > $journey.segmentList cannot be resolved to a type
> > Cannot use this in a static context
> >
> > I don't know how matching works in drools, but
> wouldn't this also be very
> > expensive? As for every match of Segment ( ) the
> segmentList has to be
> > iterated two times. These lists can get very long. A
> cheap approach would
> > be
> > if the from statement would "know" the index
> of the Segment () matched. I
> > was hoping this would be possible.
> >
> >
> > Regards,
> >
> > Chris
> >
> >
> > Greg Barton wrote:
> > >
> > > You can't do
> $journey.segmentList.indexOf(this) and
> > > $journey.segmentList.indexOf($segment), even in
> an eval?
> > >
> > > --- On Mon, 11/3/08, CSchr
> <christian.schrinner(a)sbb.ch> wrote:
> > >
> > >> From: CSchr
> <christian.schrinner(a)sbb.ch>
> > >> Subject: [rules-users] Newbie question on
> accessing predecessor and
> > >> successor in a list
> > >> To: rules-users(a)lists.jboss.org
> > >> Date: Monday, November 3, 2008, 9:56 AM
> > >> Hi everyone!
> > >>
> > >> I'm relatively new to Drools and rule
> languages.
> > >>
> > >> I'm wondering if it is possible to access
> the
> > >> predecessor and successor in a
> > >> match using from operator on an (Array)List.
> I have
> > >> something like this
> > >> (simplified):
> > >>
> > >> ...
> > >> $segment : Segment( countries contains
> Country.Switzerland
> > >> && ... ) from
> > >> $journey.segmentList
> > >>
> > >> $preSegment : Segment ( indexOf(this) ==
> indexOf($segment)
> > >> - 1,
> > >> countries not
> contains
> > Country.Switzerland
> > >> && ...
> > >> ) from $journey.segmentList
> > >>
> > >> I need something like indexOf() for the exact
> predecessor
> > >> of the matched
> > >> segment.
> > >>
> > >> If the matched business object was an element
> of a double
> > >> linked list it
> > >> would be easy. Unfortunately I don't have
> the luxury to
> > >> change the business
> > >> object into knowing it's predecessor or
> successor. I
> > >> have to prove that we
> > >> could write our java coded business rules in
> Drools rule
> > >> language without
> > >> changing the business object model.
> > >>
> > >> Thanks in advance,
> > >>
> > >> Chris
> > >>
> > >>
> > >> --
> > >> View this message in context:
> > >>
> >
>
http://www.nabble.com/Newbie-question-on-accessing-predecessor-and-succes...
> > >> Sent from the drools - user mailing list
> archive at
> > >> Nabble.com.
> > >>
> > >>
> _______________________________________________
> > >> rules-users mailing list
> > >> rules-users(a)lists.jboss.org
> > >>
> https://lists.jboss.org/mailman/listinfo/rules-users
> > >
> > >
> > >
> > > _______________________________________________
> > > rules-users mailing list
> > > rules-users(a)lists.jboss.org
> > >
> https://lists.jboss.org/mailman/listinfo/rules-users
> > >
> > >
> >
> > --
> > View this message in context:
> >
>
http://www.nabble.com/Newbie-question-on-accessing-predecessor-and-succes...
> > Sent from the drools - user mailing list archive at
> Nabble.com.
> >
> > _______________________________________________
> > rules-users mailing list
> > rules-users(a)lists.jboss.org
> > https://lists.jboss.org/mailman/listinfo/rules-users
> >
>
>
>
> --
> Edson Tirelli
> JBoss Drools Core Development
> JBoss, a division of Red Hat @ www.jboss.com
> _______________________________________________
> rules-users mailing list
> rules-users(a)lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/rules-users
_______________________________________________
rules-users mailing list
rules-users(a)lists.jboss.org
https://lists.jboss.org/mailman/listinfo/rules-users
--
View this message in context:
http://www.nabble.com/Newbie-question-on-accessing-predecessor-and-succes...
Sent from the drools - user mailing list archive at Nabble.com.
_______________________________________________
rules-users mailing list
rules-users(a)lists.jboss.org
https://lists.jboss.org/mailman/listinfo/rules-users
6:31 p.m.
I agree. Control objects are often necessary, or at least an easier way to solve a
problem than the alternatives. However, being forced to clone your business model for
rule execution is highly undesirable. That's one reason I like drools. Rule systems
that force you to recreate clone your business model just to use rules introduce an undue
burden, both in processing efficiency and maintainability.
--- On Tue, 11/4/08, CSchr <christian.schrinner(a)sbb.ch> wrote:
From: CSchr <christian.schrinner(a)sbb.ch>
Subject: Re: [rules-users] Newbie question on accessing predecessor and successor in a
list
To: rules-users(a)lists.jboss.org
Date: Tuesday, November 4, 2008, 10:58 AM
Yes that's correct. No way to change the model yet. But
I think I could
introduce additional objects and could even
"clone" the business objects
into more convenient objects just for rule evaluation. But
this would be my
least prefered solution as it would introduce a layer of
transformation and
a parallel (mirror) model that needs to be updated whenever
the business
model changes in future releases.
Regards,
Chris
Greg Barton wrote:
>
> I think you'd have to toss in ControlFact
instances with positions from 1
> to journey.segmentList.size-1 for this to work.
Otherwise the evaluation
> of the journey.segmentList would halt on the first
failure of the rule to
> match. Then the modify block wouldn't be needed
in the action.
>
> Also, CSchr, you mentioned that the business model
could not be altered.
> Does that mean you can't use additional objects
like control facts?
>
> --- On Tue, 11/4/08, Edson Tirelli
<tirelli(a)post.com> wrote:
>
>> From: Edson Tirelli <tirelli(a)post.com>
>> Subject: Re: [rules-users] Newbie question on
accessing predecessor and
>> successor in a list
>> To: "Rules Users List"
<rules-users(a)lists.jboss.org>
>> Date: Tuesday, November 4, 2008, 8:56 AM
>> Christian,
>>
>> My guess is that there are better approaches to
do what
>> you want (i.e.,
>> write your business rules) without using specific
indexes
>> in a list, since
>> that is usually a sign of trying to use a
imperative
>> algorithm in a
>> declarative engine.
>> If you can share a mock of what your business
rule is,
>> maybe we can help
>> more.
>>
>> Having said that, about your questions:
>>
>> * You can use eval inside patterns. Just remember
that
>> eval() uses a code
>> block in the same dialect you are using to write
your rules
>> (default is
>> java). So, $journey.segmentList is probably not
valid in
>> java (since
>> segmentList is probably private attribute), but is
valid in
>> MVEL that
>> transparently call getSegmentList(). So, either
change your
>> expression to a
>> correct java expression or change the rule dialect
to MVEL.
>>
>> * DISCLAIMER: THIS IS REALLY BAD PRACTICE: if you
really
>> want to emulate
>> "imperative programming" for this rule,
you need
>> a control fact to keep
>> track of the index you are testing:
>>
>> rule "Children: do not do this at home,
unless your
>> parents says it is ok"
>> when
>> $cf : ControlFact( $pos : position <
>> $journey.segmentList.size )
>> $s : Segment( countries contains
Country.Switzerland,
>> ... ) from
>> $journey.segmentList[$pos]
>> $ps : Segment( countries not contains
>> Country.Switzerland, ... ) from
>> $journey.segmentList[$pos-1]
>> then
>> // do something
>> // and also update control fact
>> modify( $cf ) { setPosition( $pos + 1 ) }
>> end
>>
>> Initialize control fact with position number 1 and
it
>> should be fine, but I
>> did not tested the above rule.
>>
>> []s
>> Edson
>>
>>
>> 2008/11/4 CSchr <christian.schrinner(a)sbb.ch>
>>
>> >
>> > Thanks Greg for your fast reply.
Unfortunately I do
>> not get this to work:
>> >
>> > $preSegment : Segment (
>> >
>> $journey.segmentList.indexOf(this) ==
>> > ($journey.segmentList.indexOf($segment) - 1),
>> > countries not contains
>> Country.Switzerland && ...
>> > ) from
$journey.segmentList
>> >
>> > Compiler throws:
>> >
>> > [36,48]: unknown:36:48 Unexpected token
>> 'this'[36,98]: unknown:36:98
>> > Unexpected token '$segment'
>> >
>> > Is it possible to use eval() inside Segment
()?
>> >
>> > With eval the compiler throws something like
this:
>> >
>> > $journey.segmentList cannot be resolved to a
type
>> > Cannot use this in a static context
>> >
>> > I don't know how matching works in
drools, but
>> wouldn't this also be very
>> > expensive? As for every match of Segment ( )
the
>> segmentList has to be
>> > iterated two times. These lists can get very
long. A
>> cheap approach would
>> > be
>> > if the from statement would "know"
the index
>> of the Segment () matched. I
>> > was hoping this would be possible.
>> >
>> >
>> > Regards,
>> >
>> > Chris
>> >
>> >
>> > Greg Barton wrote:
>> > >
>> > > You can't do
>> $journey.segmentList.indexOf(this) and
>> > > $journey.segmentList.indexOf($segment),
even in
>> an eval?
>> > >
>> > > --- On Mon, 11/3/08, CSchr
>> <christian.schrinner(a)sbb.ch> wrote:
>> > >
>> > >> From: CSchr
>> <christian.schrinner(a)sbb.ch>
>> > >> Subject: [rules-users] Newbie
question on
>> accessing predecessor and
>> > >> successor in a list
>> > >> To: rules-users(a)lists.jboss.org
>> > >> Date: Monday, November 3, 2008, 9:56
AM
>> > >> Hi everyone!
>> > >>
>> > >> I'm relatively new to Drools and
rule
>> languages.
>> > >>
>> > >> I'm wondering if it is possible
to access
>> the
>> > >> predecessor and successor in a
>> > >> match using from operator on an
(Array)List.
>> I have
>> > >> something like this
>> > >> (simplified):
>> > >>
>> > >> ...
>> > >> $segment : Segment( countries
contains
>> Country.Switzerland
>> > >> && ... ) from
>> > >> $journey.segmentList
>> > >>
>> > >> $preSegment : Segment (
indexOf(this) ==
>> indexOf($segment)
>> > >> - 1,
>> > >>
countries not
>> contains
>> > Country.Switzerland
>> > >> && ...
>> > >> ) from
$journey.segmentList
>> > >>
>> > >> I need something like indexOf() for
the exact
>> predecessor
>> > >> of the matched
>> > >> segment.
>> > >>
>> > >> If the matched business object was
an element
>> of a double
>> > >> linked list it
>> > >> would be easy. Unfortunately I
don't have
>> the luxury to
>> > >> change the business
>> > >> object into knowing it's
predecessor or
>> successor. I
>> > >> have to prove that we
>> > >> could write our java coded business
rules in
>> Drools rule
>> > >> language without
>> > >> changing the business object model.
>> > >>
>> > >> Thanks in advance,
>> > >>
>> > >> Chris
>> > >>
>> > >>
>> > >> --
>> > >> View this message in context:
>> > >>
>> >
>>
http://www.nabble.com/Newbie-question-on-accessing-predecessor-and-succes...
>> > >> Sent from the drools - user mailing
list
>> archive at
>> > >> Nabble.com.
>> > >>
>> > >>
>> _______________________________________________
>> > >> rules-users mailing list
>> > >> rules-users(a)lists.jboss.org
>> > >>
>>
https://lists.jboss.org/mailman/listinfo/rules-users
>> > >
>> > >
>> > >
>> > >
_______________________________________________
>> > > rules-users mailing list
>> > > rules-users(a)lists.jboss.org
>> > >
>>
https://lists.jboss.org/mailman/listinfo/rules-users
>> > >
>> > >
>> >
>> > --
>> > View this message in context:
>> >
>>
http://www.nabble.com/Newbie-question-on-accessing-predecessor-and-succes...
>> > Sent from the drools - user mailing list
archive at
>> Nabble.com.
>> >
>> >
_______________________________________________
>> > rules-users mailing list
>> > rules-users(a)lists.jboss.org
>> >
https://lists.jboss.org/mailman/listinfo/rules-users
>> >
>>
>>
>>
>> --
>> Edson Tirelli
>> JBoss Drools Core Development
>> JBoss, a division of Red Hat @ www.jboss.com
>> _______________________________________________
>> rules-users mailing list
>> rules-users(a)lists.jboss.org
>>
https://lists.jboss.org/mailman/listinfo/rules-users
>
>
>
> _______________________________________________
> rules-users mailing list
> rules-users(a)lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/rules-users
>
>
--
View this message in context:
http://www.nabble.com/Newbie-question-on-accessing-predecessor-and-succes...
Sent from the drools - user mailing list archive at
Nabble.com.
_______________________________________________
rules-users mailing list
rules-users(a)lists.jboss.org
https://lists.jboss.org/mailman/listinfo/rules-users
5:40 p.m.
Thank you! You are right, I should not try this at home ;)
To explain the rule, I have to explain the relevant business objects first:
A Journey contains consecutive Segments. If you interrupt your Journey to
change transportation type (on foot, train, car, bus, ship, etc.) or vehicle
(e.g. another train) you change between Segments. A Segment takes you
through one or more Country(ies).
The rule is something like this:
Find a Segment in a Journey which is of a special type T1 and is completely
in Country C1. If this Segment connects to another Segment which is of type
T2 and is at least partly or completely not in C1 then the rule fires.
Thanks everyone for your help. I think I have found the solution in the our
model. We have segment ids unique to each journey which form a natural
order. So I can check for id-1 and id+1. Did not notice this before. These
ids were never used in Java based rules implementation. So it's a workaround
without solving the actual problem ;)
Regards,
Christian
Edson Tirelli-3 wrote:
Christian,
My guess is that there are better approaches to do what you want (i.e.,
write your business rules) without using specific indexes in a list, since
that is usually a sign of trying to use a imperative algorithm in a
declarative engine.
If you can share a mock of what your business rule is, maybe we can
help
more.
Having said that, about your questions:
* You can use eval inside patterns. Just remember that eval() uses a code
block in the same dialect you are using to write your rules (default is
java). So, $journey.segmentList is probably not valid in java (since
segmentList is probably private attribute), but is valid in MVEL that
transparently call getSegmentList(). So, either change your expression to
a
correct java expression or change the rule dialect to MVEL.
* DISCLAIMER: THIS IS REALLY BAD PRACTICE: if you really want to emulate
"imperative programming" for this rule, you need a control fact to keep
track of the index you are testing:
rule "Children: do not do this at home, unless your parents says it is ok"
when
$cf : ControlFact( $pos : position < $journey.segmentList.size )
$s : Segment( countries contains Country.Switzerland, ... ) from
$journey.segmentList[$pos]
$ps : Segment( countries not contains Country.Switzerland, ... ) from
$journey.segmentList[$pos-1]
then
// do something
// and also update control fact
modify( $cf ) { setPosition( $pos + 1 ) }
end
Initialize control fact with position number 1 and it should be fine, but
I
did not tested the above rule.
[]s
Edson
2008/11/4 CSchr <christian.schrinner(a)sbb.ch>
>
> Thanks Greg for your fast reply. Unfortunately I do not get this to work:
>
> $preSegment : Segment (
> $journey.segmentList.indexOf(this) ==
> ($journey.segmentList.indexOf($segment) - 1),
> countries not contains Country.Switzerland && ...
> ) from $journey.segmentList
>
> Compiler throws:
>
> [36,48]: unknown:36:48 Unexpected token 'this'[36,98]: unknown:36:98
> Unexpected token '$segment'
>
> Is it possible to use eval() inside Segment ()?
>
> With eval the compiler throws something like this:
>
> $journey.segmentList cannot be resolved to a type
> Cannot use this in a static context
>
> I don't know how matching works in drools, but wouldn't this also be very
> expensive? As for every match of Segment ( ) the segmentList has to be
> iterated two times. These lists can get very long. A cheap approach would
> be
> if the from statement would "know" the index of the Segment () matched. I
> was hoping this would be possible.
>
>
> Regards,
>
> Chris
>
>
> Greg Barton wrote:
> >
> > You can't do $journey.segmentList.indexOf(this) and
> > $journey.segmentList.indexOf($segment), even in an eval?
> >
> > --- On Mon, 11/3/08, CSchr <christian.schrinner(a)sbb.ch> wrote:
> >
> >> From: CSchr <christian.schrinner(a)sbb.ch>
> >> Subject: [rules-users] Newbie question on accessing predecessor and
> >> successor in a list
> >> To: rules-users(a)lists.jboss.org
> >> Date: Monday, November 3, 2008, 9:56 AM
> >> Hi everyone!
> >>
> >> I'm relatively new to Drools and rule languages.
> >>
> >> I'm wondering if it is possible to access the
> >> predecessor and successor in a
> >> match using from operator on an (Array)List. I have
> >> something like this
> >> (simplified):
> >>
> >> ...
> >> $segment : Segment( countries contains Country.Switzerland
> >> && ... ) from
> >> $journey.segmentList
> >>
> >> $preSegment : Segment ( indexOf(this) == indexOf($segment)
> >> - 1,
> >> countries not contains
> Country.Switzerland
> >> && ...
> >> ) from $journey.segmentList
> >>
> >> I need something like indexOf() for the exact predecessor
> >> of the matched
> >> segment.
> >>
> >> If the matched business object was an element of a double
> >> linked list it
> >> would be easy. Unfortunately I don't have the luxury to
> >> change the business
> >> object into knowing it's predecessor or successor. I
> >> have to prove that we
> >> could write our java coded business rules in Drools rule
> >> language without
> >> changing the business object model.
> >>
> >> Thanks in advance,
> >>
> >> Chris
> >>
> >>
> >> --
> >> View this message in context:
> >>
>
http://www.nabble.com/Newbie-question-on-accessing-predecessor-and-succes...
> >> Sent from the drools - user mailing list archive at
> >> Nabble.com.
> >>
> >> _______________________________________________
> >> rules-users mailing list
> >> rules-users(a)lists.jboss.org
> >> https://lists.jboss.org/mailman/listinfo/rules-users
> >
> >
> >
> > _______________________________________________
> > rules-users mailing list
> > rules-users(a)lists.jboss.org
> > https://lists.jboss.org/mailman/listinfo/rules-users
> >
> >
>
> --
> View this message in context:
>
http://www.nabble.com/Newbie-question-on-accessing-predecessor-and-succes...
> Sent from the drools - user mailing list archive at Nabble.com.
>
> _______________________________________________
> rules-users mailing list
> rules-users(a)lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/rules-users
>
--
Edson Tirelli
JBoss Drools Core Development
JBoss, a division of Red Hat @ www.jboss.com
_______________________________________________
rules-users mailing list
rules-users(a)lists.jboss.org
https://lists.jboss.org/mailman/listinfo/rules-users
--
View this message in context:
http://www.nabble.com/Newbie-question-on-accessing-predecessor-and-succes...
Sent from the drools - user mailing list archive at Nabble.com.
4:12 p.m.
Use $this. (Note the $ at the beginning)
Yes, inline evals are allowed. See section 6.5.2.1.2 in the docs:
http://downloads.jboss.com/drools/docs/4.0.7.19894.GA/html_single/index.html
--- On Tue, 11/4/08, CSchr <christian.schrinner(a)sbb.ch> wrote:
From: CSchr <christian.schrinner(a)sbb.ch>
Subject: Re: [rules-users] Newbie question on accessing predecessor and successor in a
list
To: rules-users(a)lists.jboss.org
Date: Tuesday, November 4, 2008, 1:45 AM
Thanks Greg for your fast reply. Unfortunately I do not get
this to work:
$preSegment : Segment (
$journey.segmentList.indexOf(this)
==
($journey.segmentList.indexOf($segment) - 1),
countries not contains
Country.Switzerland && ...
) from $journey.segmentList
Compiler throws:
[36,48]: unknown:36:48 Unexpected token
'this'[36,98]: unknown:36:98
Unexpected token '$segment'
Is it possible to use eval() inside Segment ()?
With eval the compiler throws something like this:
$journey.segmentList cannot be resolved to a type
Cannot use this in a static context
I don't know how matching works in drools, but
wouldn't this also be very
expensive? As for every match of Segment ( ) the
segmentList has to be
iterated two times. These lists can get very long. A cheap
approach would be
if the from statement would "know" the index of
the Segment () matched. I
was hoping this would be possible.
Regards,
Chris
Greg Barton wrote:
>
> You can't do $journey.segmentList.indexOf(this)
and
> $journey.segmentList.indexOf($segment), even in an
eval?
>
> --- On Mon, 11/3/08, CSchr
<christian.schrinner(a)sbb.ch> wrote:
>
>> From: CSchr <christian.schrinner(a)sbb.ch>
>> Subject: [rules-users] Newbie question on
accessing predecessor and
>> successor in a list
>> To: rules-users(a)lists.jboss.org
>> Date: Monday, November 3, 2008, 9:56 AM
>> Hi everyone!
>>
>> I'm relatively new to Drools and rule
languages.
>>
>> I'm wondering if it is possible to access the
>> predecessor and successor in a
>> match using from operator on an (Array)List. I
have
>> something like this
>> (simplified):
>>
>> ...
>> $segment : Segment( countries contains
Country.Switzerland
>> && ... ) from
>> $journey.segmentList
>>
>> $preSegment : Segment ( indexOf(this) ==
indexOf($segment)
>> - 1,
>> countries not contains
Country.Switzerland
>> && ...
>> ) from $journey.segmentList
>>
>> I need something like indexOf() for the exact
predecessor
>> of the matched
>> segment.
>>
>> If the matched business object was an element of a
double
>> linked list it
>> would be easy. Unfortunately I don't have the
luxury to
>> change the business
>> object into knowing it's predecessor or
successor. I
>> have to prove that we
>> could write our java coded business rules in
Drools rule
>> language without
>> changing the business object model.
>>
>> Thanks in advance,
>>
>> Chris
>>
>>
>> --
>> View this message in context:
>>
http://www.nabble.com/Newbie-question-on-accessing-predecessor-and-succes...
>> Sent from the drools - user mailing list archive
at
>> Nabble.com.
>>
>> _______________________________________________
>> rules-users mailing list
>> rules-users(a)lists.jboss.org
>>
https://lists.jboss.org/mailman/listinfo/rules-users
>
>
>
> _______________________________________________
> rules-users mailing list
> rules-users(a)lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/rules-users
>
>
--
View this message in context:
http://www.nabble.com/Newbie-question-on-accessing-predecessor-and-succes...
Sent from the drools - user mailing list archive at
Nabble.com.
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10 comments
4 participants
participants (4)
-
CSchr -
Earnest Dyke -
Edson Tirelli -
Greg Barton