Eclipse Community Forums: TMF (Xtext) » Sharing rules' bodies

Help

Home

Home » Modeling » TMF (Xtext) » Sharing rules' bodies

Show: Today's Messages :: Show Polls :: Message Navigator

Sharing rules' bodies [message #1717217]

Thu, 10 December 2015 19:37

Ernesto Posse

Messages: 438
Registered: March 2011

Senior Member

I have a language where I want expressions like this:

thing { part x;  part y; }

stuff Name { part x;  part y; }

where 'thing' and 'stuff' are separate constructs whose body shares the same syntax.

The language is created from an existing Ecore meta-model where "Thing" has a "stuff" property of type "Stuff". "Stuff" has a list of "parts".

I could write the following grammar:

ThingContents return Stuff:
  '{' (parts+=Part)* '}'

Part:
  'part' name=ID ';';

Thing:
  'thing' stuff=ThingContents;

Stuff:
  'stuff' name=ID '{' (parts+=Part)* '}';

But this grammar duplicates the contents of "thing" and "stuff".

I would like to be able to avoid duplication in my grammar. Can this be accomplished? If so how?

I tried the following:

Contents return Stuff:
  '{' (parts+=Part)* '}'

Part:
  'part' name=ID ';';

Thing:
  'thing' stuff=Contents;

Stuff:
  'stuff' name=ID Contents;

but it fails on the "Stuff" rule with "An unassigned rule call is not allowed, when the 'current' was already created."

Is there any way to share the body of a rule among different rules?

Report message to a moderator

Re: Sharing rules' bodies [message #1717222 is a reply to message #1717217]

Thu, 10 December 2015 19:59

Stefan Oehme

Messages: 159
Registered: April 2010
Location: Kiel

Senior Member

Hi Ernesto,

in Xtext 2.9 you can define a parser rule fragment

fragment Contents :
  '{' (parts+=Part)* '}'
;

And then use it like this:

Thing:
  'thing' stuff=ThingContents;

ThingContents:
  Contents
;

Stuff:
  'stuff' name=ID Contents;

Ideally, I would get rid of the "ThingContents" indirection in the ecore model, but maybe it's needed for reasons I don't see =)

Like this:

Thing:
  'thing' Contents

Stuff:
  'stuff' name=ID Contents;

Cheers,
Stefan

[Updated on: Thu, 10 December 2015 20:01]

Report message to a moderator

Re: Sharing rules' bodies [message #1717226 is a reply to message #1717222]

Thu, 10 December 2015 20:37

Ernesto Posse

Messages: 438
Registered: March 2011

Senior Member

Great! But that's not available in 2.8.4, is it?

Report message to a moderator

Re: Sharing rules' bodies [message #1717250 is a reply to message #1717226]

Fri, 11 December 2015 05:27

Christian Dietrich

Messages: 14665
Registered: July 2009

Senior Member

No this is a xtext 2.9 feature

Twitter : @chrdietrich
Blog : https://www.dietrich-it.de

Report message to a moderator

Previous Topic:	Defining Cardinality Elegantly
Next Topic:	Fatal problem with TreeAppendable

Goto Forum:

-=] Back to Top [=-

[ Syndicate this forum (XML) ] [

]

Current Time: Thu Apr 25 14:30:12 GMT 2024

.:: Contact :: Home ::.

Breadcrumbs

Sign up to our Newsletter