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"Hiding" a rule [message #871446]

Sun, 13 May 2012 19:56

$Haravikk Kh\'arr is currently offline$ Haravikk Kh\'arr

Messages: 19
Registered: February 2011

Junior Member

Hi there,

Been a while since I touched Xtext, but I'm back to working on a project I put on hiatus for a while.

Anyway, one thing that I never quite decided on a solution for, and still would like to solve, is how to *remove* a rule from an extended grammar.

For example; if I'm building a grammar that is an extension of Xbase, then is it possible to prevent the use of closures by somehow making that rule unusable.

I know how to override a rule, but I'm not sure I'd go about using that to prevent a rule from being used, other than to type some kind of garbage keyword in that nobody's likely to use.

[Updated on: Sun, 13 May 2012 19:57]

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Re: "Hiding" a rule [message #871449 is a reply to message #871446]

Sun, 13 May 2012 20:15

$Haravikk Kh\'arr is currently offline$ Haravikk Kh\'arr

Messages: 19
Registered: February 2011

Junior Member

Also as a side-note; is it possible to extend, rather than override a rule.

For example, if I wished to add a new literal type in Xbase's XLiteral rule, is it possible to somehow do the following:

XLiteral returns XExpression: XLiteral | MyNewLiteral;

Obviously the above returns an error, I'm curious to know if there's a way to refer to the Xbase version of XLiteral within my overriding XLiteral rule? Obviously it's not too hard to just copy/paste the Xbase version of XLiteral and add my changes in, but I'd rather just add mine on top, if possible.

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Re: "Hiding" a rule [message #871450 is a reply to message #871446]

Sun, 13 May 2012 20:16

Christian Dietrich

Messages: 14665
Registered: July 2009

Senior Member

Hi,

you have to adapt the calling rules as well. e.g.

XLiteral returns XExpression:
	XBooleanLiteral |
	XIntLiteral |
	XNullLiteral |
	XStringLiteral |
	XTypeLiteral
;

XConstructorCall returns XExpression:
	{XConstructorCall}
	'new' constructor=[types::JvmConstructor|QualifiedName] 
	('<' typeArguments+=JvmArgumentTypeReference (',' typeArguments+=JvmArgumentTypeReference)* '>')?
	'(' 
		(
		    arguments+=XShortClosure
		  |	arguments+=XExpression (',' arguments+=XExpression)*
		)? 
	')';

...

~Christian

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

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