[rules-users] Translate Drools to CLIPS rules

[Mark Proctor]

On 31 May 2013, at 07:43, Wolfgang Laun <wolfgang.laun at gmail.com> wrote:

> On 31/05/2013, Mark Proctor <mproctor at codehaus.org> wrote:
>> 
>> On 30 May 2013, at 23:36, "Stadin, Benjamin"
>> <Benjamin.Stadin at heidelberg-mobil.com> wrote:
>> 
>>> I'd be  willing to get involved, but since you mention clp to drl only,
>>> will it also be possibly to convert drl to clp?
>> yes. There is already a "DrlDumper" that takes a Rule and dumps it to a
>> string, using a bunch of recursive mvel templates.  You can copy/paste this
>> and have it dump to CLP instead.
>> https://github.com/droolsjbpm/drools/blob/master/drools-compiler/src/main/java/org/drools/compiler/lang/DrlDumper.java
>> https://github.com/droolsjbpm/drools/blob/master/drools-compiler/src/main/resources/org/drools/compiler/lang/drl.mvel
>> 
>> if you change the drl.mvel to a clp.mvel and change the text it outputs, you
>> have yourself a CLP<->DRL translator. The caveat ofcourse is you must keep
>> to the common base level of features between the two systems.
> 
> The first if is hiding an enormous amount of work. The template
> drl.mvel appears to take arbitrarily long snippets of Java (or MVEL)
> code and simply copy it into the result text: function bodies, eval
> expressions, accumulate init,  action and result code, and all of the
> RHS. I'm not saying it can't be done, but it sure will keep you busy
> for quite some time.
> 
> Translating Java expressions to CLP can't be done based on abstract
> syntax. Consider, for instance,
>   stdout.println( a + b );
> To be able to translate this to
>   printout( t (+ a b) )
> you'd have to make sure that stdout is indeed the same as router t and
> that a and b are numeric quantities - otherwise str-cat would be
> required.
> 
> Copy/paste with a whole lot of magic ;-)
yeah the LHS isn't so had, if they stick to simple patterns, the RHS is a whole different kettle of fish :) You can load the RHS into an antlr based java.g grammar, and try and translate it - but it wouldn't be fun.

So probably best first to stick to clp->drl, which is more straight forward. Besides, once you are on DRL, why would you want to go back to CLP :)

Mark
> 
> Wolfgang
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