Edson,

On 6 May 2011 01:14, Edson Tirelli <ed.tirelli@gmail.com> wrote:

   Wolfgang,

   These are remaining bugs that must be fixed before final. Goal is to support free form expressions as long as they return a boolean value (for traditional constraints), or any value (for positional). Period.

(Well, as it's past 5.2.0M2...)

Given that any expression is valid, will there still be a distinction w.r.t. efficiency, as there was with traditional constraints as opposed to eval()? If yes, how can I tell whether a constraint expression is "good" or "bad"?

One might assume that all legacy forms will be handled as efficiently as now, but it's possible that not only
   field == ($var + 1)
but also
   field == $var + 1
is efficient. Or, similarly,
   field == $var
and (now) also
   $var == field

But certainly not
   field - 1 == $var
Or, at least, not until some later version ;-)

I repeat this quote (from 5.2.0 Drools Introduction and General User Guide) and my question, what does it mean? Where is this "documented"? Is this somehow related to the efficiency issue?

<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>

Wolfgang

 

   Edson

2011/5/5 Wolfgang Laun <wolfgang.laun@gmail.com>

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>
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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