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LL(*)-left refactoring and cross-reference [message #1017161]

Sun, 10 March 2013 10:14

Vincent Simonet

Messages: 8
Registered: March 2013

Junior Member

Hello,

I've a language (lesscss) that requires a grammar entry like:

Statement:
  ident=IDENT term=Term 'set'
| reference=[VariableCrossReference|IDENT] term=Term 'get'
;

where Term is a recursive rule.

This rule is rejected by ANTLR because has non-LL(*) decision due to recursive rule invocations (in short, you need to parse 'set' or 'get' to decide between the first and the second alternative.

The usual way to resolve the issue with LL(*) grammars would be to make a left refactoring like:

Statement:
  ident=IDENT term=Term keywork=('set | 'get')
;

but I cannot do that with Xtext and keep the cross-reference.

Is there a way to workaround this limitation?

Thanks!

--
Vincent

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Re: LL(*)-left refactoring and cross-reference [message #1017965 is a reply to message #1017161]

Tue, 12 March 2013 21:51

Vincent Simonet

Messages: 8
Registered: March 2013

Junior Member

FYI, I found a way to solve the problem. With some hack in the scope provider, it is possible to have a cross-reference in both, i.e. to refactor the grammar definition into:

Statement:
  ident=[VariableCrossReference|IDENT] term=Term 'set'
| reference=[VariableCrossReference|IDENT] term=Term 'get'
;

and then

Statement:
 reference=[VariableCrossReference|IDENT] term=Term ('get' | 'set')
;

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