In the 5.2.0 Drools Introduction and General User Guide, there's section
2.1.3.1, Free Form expressions in Constraints (New Parser). It contains
several examples:
#1 Person( age * 2 > $anotherPersonsAge + 2 )
#2 Person( addresses["home"].streetName.startsWith( "High Park" ) )
#3 Person( isAdult() )
#1 does not compile: Unable to build constraint as 'age * 2' is invalid :
[Rule name='exa1']
#2 works - although I'd very much prefer not to be swamped with MVEL
extensions unless I ask for it.
#3 does not compile: Unable to Analyse Expression isAdult():
[Error: no such identifier: isAdult]
[Near : {... isAdult() ....}]
Neither rule name nor line number is provided.
Would it please be possible to have a precise statement what one *can* write
as a constraint?
<quote>
This was also important for us to start to move towards a single consistent
grammer for both the "when" left hand side and "then" right hand side.
</quote>
It seems that example #2 increases the grammar gap because the constraint
expression can certainly not used on the RHS.
<quote>
As previously we had to document the restricted limitations of a field
constraint on the LHS compared to expressions used inside of an 'eval' or
used on the RHS.
</quote>
I'm sorry, but I do not understand the meaning of this sentence. What does
it mean, please?
Cheers
Wolfgang
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