[news.eclipse.modeling.mdt.ocl] Re: custom operators and functions using

[edamagg@xxxxxxxxxx (Elio Damaggio)]

Hi Christian,

I was able to have the operator work :)

How is the situation for unary operators?
Is there a way to define those for custom datatypes?
Thanks,

Elio


Christian W. Damus wrote:

> Hi, Ed, Elio,

> Yes, OCL is trained to look for Java names "plus", "minus", "lessThan",
> "greaterThan", etc. to implement these symbolic operators, but it does
> expect to find the symbolic names (e.g., "+", "<") in the model's
> EClass.  The "<" / "lessThan" operation is particularly handy because it
> allows your type to be used in "orderedBy" iterators.

> One of the callOperation() or some such methods in the
> EvaluationEnvironment type hierarchy has the mapping from symbolic to
> Java names, in looking up the Method objects to invoke reflectively.  I
> should, of course, have documented it in the SDK's developer guide,
> too  :-(

> Cheers,

> Christian


> On Sat, 2009-08-29 at 06:52 +0100, Ed Willink wrote:

> > Hi Elio, Ed
> >
> > [Ed: you may be able to provide a simple solution for b).]
> >
> > a) parser modification
> >
> > The parser is intended to be extended rather than modified. Be very wary 
> > of modifying; you will have te re-engineer each time MDT-OCL improves. 
> > That said we are in the process of migrating from LPG 1 to LPG 2,
> > https://bugs.eclipse.org/bugs/show_bug.cgi?id=242153, which will require 
> > about four trivial edit procedures to existing extensions.
> >
> > b) operators
> >
> > In your Ecore model of custom data types (EClass not EDataType) you can 
> > add operations such as "+", which you can then use them naturally in 
> > OCL. Unfortunately these give a validation error in EMF so you cannot 
> > genModel them.
> >
> > I'm not sure if the situation is any better for a UML model.
> >
> > This is a spelling problem I've been considering already: For OCL it 
> > must be "+" for Java it must be perhaps "_plus". (OMG) OCL needs to 
> > specify an encoding scheme for awkward characters and to specify a 
> > concrete syntax access scheme. MDT-OCL supports access via double quotes 
> > e.g:
> >
> > def: "+"(d : Date) ...
> >
> > I'm afraid I don't know of any solution to making Date + Date work today.
> >
> > The XSD support for EMF provides a form of renaming. I've copied this to 
> > Ed Merks who may be able to explain how it could be exploited.
> >
> > c) call path
> >
> > I'm not very familiar with the EvaluationEnvironment, so nearly all of 
> > what I'm about to suggest may already be the current MDT-OCL functionality.
> >
> > You can introduce a derived LOTREnvironment which is created at each 
> > stage of evaluation, with a reference to its outer context. At any point 
> > these references give you the call path. You can then add custom methods 
> > to evaluate any function of the call path that you like. Perhaps you 
> > encapsulate these all in a richer Environment object and implement just 
> > a single .oclEnvironment() method to access it. If you get this working 
> > it might make for a useful contribution to MDT-OCL and a submission for 
> > a future OCL specification.
> >
> > 	Regards
> >
> > 		Ed Willink
> >
> > Elio Damaggio wrote:
> > > Hi all,
> > > 
> > > I am modifying the OCL parser/evaluator in order to (besides other 
things):
> > > 
> > > * include a series of time related datatypes (Date, Time, Duration, 
> > > Timestamp). These datatypes should have standard infix operators (+, -, 
> > > ..) like integers and so on... I think I have to modify the 
> > > EvaluationVisitor. Is this the best course of action?
> > > 
> > > * include predefined methods that, if applied on an attribute, have 
> > > access to the model information of that attribute (i.e. which class they 
> > > belong, in addition to the actual instance).
> > > For instance, lets assume book have an attribute called author. And the 
> > > "LOTR" book instance has "Tolkien" as its author attribute. Then the 
> > > predefined method LOTR.author.info() should be able to know that it is 
> > > invoked on the "author" attribute of a "book" class.
> > > Do you have any idea on how to implement these methods?
> > > 
> > > Thank you all,
> > > 
> > > Elio
> > >