[jboss-jira] [JBoss JIRA] Commented: (JBRULES-1083) Brackets are not always optional for non-existential quantifier "not"

[Edson Tirelli (JIRA)]

    [ http://jira.jboss.com/jira/browse/JBRULES-1083?page=comments#action_12372969 ] 
            
Edson Tirelli commented on JBRULES-1083:
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I think for this case we should fix documentation only and keep parser behavior as it is right now, i.e., for "not" and "exists", the brackets are option only if they are followed by a single pattern. 

The current grammar rules are:

LHS_NOT::= 'not' ( '(' <conditional_element> ')' ) | <pattern>
LHS_EXISTS::= 'exists' ( '(' <conditional_element> ')' ) | <pattern>

So, the following is valid:

not Bus()
not ( Bus() )  // brackets are optional for single pattern.

Any other following conditional element will require the brackets. Following are all valid:

not( Bus() and Driver() )
not( Bus() from $buses )
not( Bus() and not Driver() )
not( Bus() and not( Driver() ) )

Please note that the following is valid and require the ():

not( exists( Bus() ) )

But the above is Semantically EQUIVALENT as:

not( Bus() )



> Brackets are not always optional for non-existential quantifier "not" 
> ----------------------------------------------------------------------
>
>                 Key: JBRULES-1083
>                 URL: http://jira.jboss.com/jira/browse/JBRULES-1083
>             Project: JBoss Rules
>          Issue Type: Bug
>      Security Level: Public(Everyone can see) 
>          Components: Drl Parser/Builder
>    Affects Versions:  4.0.0.GA
>            Reporter: Markus Reitz
>         Assigned To: Mark Proctor
>            Priority: Minor
>             Fix For: 4.0.1
>
>
> According to the documentation, brackets are optional as illustrated by
>   Example 6.37. No Busses
>   not Bus()
> In case of the rule (class SpecialString in http://jira.jboss.com/jira/browse/JBRULES-1079)
>   package test
>   rule "Brackets"
>     when
>       not exists(x : SpecialString() and
>                  forall(y : SpecialString(this!=x)
>                             SpecialString(this==y, text=="Universe")))
>     then
>       System.out.println("Condition satisfied");
>   end
> this is not true. Trying to load this rule leads to
> org.drools.rule.InvalidRulePackage: [8,8]: unknown:8:8 Unexpected token 'exists'
> at org.drools.rule.Package.checkValidity(Package.java:408)
> at org.drools.common.AbstractRuleBase.addPackage(AbstractRuleBase.java:288)
> at DroolsTest.<init>(Unknown Source)
> at DroolsTest.main(Unknown Source)
> When brackets are added:
>   package test
>   rule "Brackets"
>     when
>       not(exists(x : SpecialString() and
>                  forall(y : SpecialString(this!=x)
>                             SpecialString(this==y, text=="Universe"))))
>     then
>       System.out.println("Condition satisfied");
>   end
> rule loading works without any exceptions.

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