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Can I remove things from AST [message #886539]

Fri, 15 June 2012 06:24

Kevin Sun

Messages: 32
Registered: August 2010
Location: China

Member

I want to support conditional compiling in my language without using pre-processor.

What I did is to remove all things in the inactive area from the AST before the AST is linked.

as the code showes

protected void beforeModelLinked(EObject model,
			IDiagnosticConsumer diagnosticsConsumer) {
		for(TreeIterator<EObject> it = model.eAllContents();it.hasNext();){
			EObject obj = it.next();
			if(obj instanceof ConditionalElement){
				String target = ((ConditionalElement) obj).getTarget();
				if(defined((ConditionalElement) obj,target)){
					((ConditionalElement) obj).getFalseElements().clear();
				}else{
					((ConditionalElement) obj).getTrueElements().clear();
				}
			}
		}
		super.beforeModelLinked(model, diagnosticsConsumer);
	}

But sometimes when I edit the file, I will get exception as following. Especially when I change "#define B" to "#define BC", I will meet this problem.

org.eclipse.emf.common.util.BasicEList$BasicIndexOutOfBoundsException: index=1, size=0
at org.eclipse.emf.common.util.BasicEList.get(BasicEList.java:352)
at org.eclipse.emf.ecore.util.EContentsEList$FeatureIteratorImpl.hasNext(EContentsEList.java:484)
at org.eclipse.emf.ecore.util.EContentsEList$FeatureIteratorImpl.next(EContentsEList.java:565)
at org.eclipse.emf.common.util.AbstractTreeIterator.next(AbstractTreeIterator.java:139)
at org.xtext.example.mydsl.MyDslLinker.beforeModelLinked(MyDslLinker.java:34)

The grammar I used is:

Model:
	elements += Element*
;
Element:
	  Type
	| Var
	| ConditionalElement
	| ConditionalControl
	| Expr
;
Type:
	'type' name = ID
;
Var:
	name = ID ':' type = [Type]
;
ConditionalElement:
	'#ifdef' target = ID
	trueElements += Element *
	(
		'#else'
		falseElements += Element *
	)?
	'#endif'
;
ConditionalControl:
	'#define' name = ID
;
Expr:
	'expr' var = [Var]
;
Unused :
	t = [ConditionalControl]
;

and the test.mydsl is:

type int
i : int
expr i

#define B
#ifdef B
i1 : int
#else
i2 : intttt
#endif

#ifdef B
expr i2
expr x
#else
expr i11111 
expr x
#endif

[Updated on: Fri, 15 June 2012 06:53]

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Re: Can I remove things from AST [message #886574 is a reply to message #886539]

Fri, 15 June 2012 07:43

Sebastian Zarnekow

Messages: 3108
Registered: July 2009

Senior Member

Hi Kevin,

you should not try to modify the semantic model in the linker. That will
cause all sorts of undesired side effects. I'd recommend to filter the
linking errors or things like that instead of removing elements from the
AST.

Regards,
Sebastian
--
Need professional support for Eclipse Modeling?
Go visit: http://xtext.itemis.com

Am 15.06.12 08:24, schrieb Kevin Sun:
> I want to support conditional compiling in my language without using
> pre-processor.
>
> What I did is to remove all things in the inactive area from the AST
> before the AST is linked.
>
> as the code showes
>
>
> protected void beforeModelLinked(EObject model,
> IDiagnosticConsumer diagnosticsConsumer) {
> for(TreeIterator<EObject> it = model.eAllContents();it.hasNext();){
> EObject obj = it.next();
> if(obj instanceof ConditionalElement){
> String target = ((ConditionalElement) obj).getTarget();
> if(defined((ConditionalElement) obj,target)){
> ((ConditionalElement) obj).getFalseElements().clear();
> }else{
> ((ConditionalElement) obj).getTrueElements().clear();
> }
> }
> }
> super.beforeModelLinked(model, diagnosticsConsumer);
> }
>
>
> But sometimes when I edit the file, I will get exception:
>
> org.eclipse.emf.common.util.BasicEList$BasicIndexOutOfBoundsException:
> index=1, size=0
> at org.eclipse.emf.common.util.BasicEList.get(BasicEList.java:352)
> at
> org.eclipse.emf.ecore.util.EContentsEList$FeatureIteratorImpl.hasNext(EContentsEList.java:484)
>
> at
> org.eclipse.emf.ecore.util.EContentsEList$FeatureIteratorImpl.next(EContentsEList.java:565)
>
> at
> org.eclipse.emf.common.util.AbstractTreeIterator.next(AbstractTreeIterator.java:139)
>
> at
> org.xtext.example.mydsl.MyDslLinker.beforeModelLinked(MyDslLinker.java:34)
>
> The grammar I used is:
>
> Model:
> elements += Element*
> ;
> Element:
> Type
> | Var
> | ConditionalElement
> | ConditionalControl
> | Expr
> ;
> Type:
> 'type' name = ID
> ;
> Var:
> name = ID ':' type = [Type]
> ;
> ConditionalElement:
> '#ifdef' target = ID
> trueElements += Element *
> (
> '#else'
> falseElements += Element *
> )?
> '#endif'
> ;
> ConditionalControl:
> '#define' name = ID
> ;
> Expr:
> 'expr' var = [Var]
> ;
> Unused :
> t = [ConditionalControl]
> ;
>
>
> and the test.mydsl is:
>
> type int
> i : int
> expr i
>
> #define B
> #ifdef B
> i1 : int
> #else
> i2 : intttt
> #endif
>
> #ifdef B
> expr i2
> expr x
> #else
> expr i11111 expr x
> #endif
>

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Re: Can I remove things from AST [message #886715 is a reply to message #886574]

Fri, 15 June 2012 14:12

Kevin Sun

Messages: 32
Registered: August 2010
Location: China

Member

Thanks for your reply. I will try to filter error messages as you said. And, by making all named elements in the inactive parts has no qualified name, I can make them unreferencable by others.

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