[rules-users] Collecting properties in a rule

[Wolfgang Laun]

The rule below assumes that markets is List<Market> in Town and ids is
List<Integer> in a Market.

It does not rely on Market or even Location objects being facts, and
there's no problem if a location id is re-used in another town.

rule findThree
when
    $t: Town( $name: name, $markets: markets )
    $s: HashSet( $size: size ==3 )
            from accumulate( $m: Market() from $markets,
                             init( HashSet set = new HashSet(); )
                             action( set.addAll( $m.getIds() ); )
                             result( set ) )
then
    System.out.println( $name + " is a three-location town " + $s );
end


2011/11/14 Michael Anstis <michael.anstis at gmail.com>

> Something like this?
>
> when
>     $t : Town( )
>     $s : SuperMarket( town == $t, $lid : locationId )
>     $ls : HashSet( size == 3) from ( Location( locationId = $lid ) )
>
> I suspect Location would have to override equals and hashCode correctly.
>
> Once you have some DRL that works I'd suggest moving to Guvnor.
>
>
> On 12 November 2011 23:15, LCode <j_whittlesea at hotmail.com> wrote:
>
>> I am trying to write a rule via the guided rule editor and I am really
>> struggling.
>>
>> The following is a simplified explanation of my scenario:
>>
>> I have a model where there are lots of 'Town' objects, each town has any
>> number of 'Supermarket' objects and each supermarket has a list of
>> integers
>> 'locationID'.
>>
>> Something like this....
>>
>>        <Town>
>>                <Supermarket name = 'asda'>
>>                        <LocationID>15</LocationID>
>>                        <LocationID>18</LocationID>
>>                </Supermarket>
>>                <Supermarket name = 'tesco'>
>>                        <LocationID>13</LocationID>
>>                </Supermarket>
>>                <Supermarket name = 'lidl'>
>>                        <LocationID>13</LocationID>
>>                        <LocationID>15</LocationID>
>>                        <LocationID>18</LocationID>
>>                </Supermarket>
>>        </Town>
>>
>> (apologies to the Sainsburys shoppers!!)
>>
>> I need to write a rule that fires when there are precisely 3 unique
>> location
>> ID's in the whole town.
>>
>> So in the example above the complete list of locationIDs would be 13, 13,
>> 15, 15, 18, 18
>> With the following unique numbers 13, 15, 18
>> therefore the rule would fire as there are 3 unique numbers.
>>
>> I hope that makes some sense.
>>
>> I understand that I should collect the locationIDs into a java.util.Set in
>> order to count unique entries and I can collect together all supermarkets
>> into an arraylist. However I cannot for the life of me seem to collect
>> LocationID across all supermarkets.
>>
>> Thank you so much in anticipation, I realise this was rather long-winded!
>>
>> --
>> View this message in context:
>> http://drools.46999.n3.nabble.com/Collecting-properties-in-a-rule-tp3503523p3503523.html
>> Sent from the Drools: User forum mailing list archive at Nabble.com.
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>>
>
>
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