Eclipse Community Forums: TMF (Xtext) » How to restrict a rule

Home » Modeling » TMF (Xtext) » How to restrict a rule

How to restrict a rule [message #1058265]

Mon, 13 May 2013 08:16

Eclipse User

I have something like,

Model
exp1= EXPRESSION '+' exp2=EXPRESSION

where EXPRESSION handles all kind of possible cases that i require.

Now the problem is that '+' is also part of an expression, and exp1 basically spans across the '+' symbol and consumes the exp2 as well.

is it possible to do this in some other way?

Thanks,
Rohit

Re: How to restrict a rule [message #1058447 is a reply to message #1058265]

Tue, 14 May 2013 03:19

Eclipse User

Before you can answer this question you need to decide for yourself how the compiler should decide which expression belongs in which side of the AST. For example, should it parse:

a + b + c

exp1='a' '+' exp2='b + c'

exp1='a + b' '+' exp2='c'

Until you can decide this for yourself, there isn't a general case answer to your problem.

It may be the case that you are trying to put too much validation into the parser. Consider parsing 'EXPRESSION + EXPRESSION' in a single rule, rather than two, then deciding in your model validation and/or inference which version of the rule is intended (according to rules of your own choosing).

Hope that helps!

Re: How to restrict a rule [message #1058461 is a reply to message #1058447]

Tue, 14 May 2013 04:43

Eclipse User

This might help as well
http://blog.efftinge.de/2010/08/parsing-expressions-with-xtext.html

Previous Topic:	Developing custom xtext editor
Next Topic:	Generate mydsl Plug-in with Updatesite

Goto Forum:

-=] Back to Top [=-

Current Time: Sat Jul 12 17:17:25 EDT 2025

.:: Contact :: Home ::.

Breadcrumbs

Sign up to our Newsletter