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backtracking problem while generate grammar [message #730963]

Thu, 29 September 2011 15:50

samir

Messages: 27
Registered: September 2011

Junior Member

hi

I am a new xtext user, I describe my problem,

this is my grammar:

Term : Var | Abs | App;
Var : name = ID;
Abs : '\\' name = ID'.'(termList +=Term)+ ;
App : '(' t1 = Term t2 =Term ')';

when I try to generate xtext artifacts eclipse gives me this error

error(211): ../example.ui/src-gen/org/xtext/example/mydsl/ui/contentassist/antlr/internal/InternalMyDsl.g:317:33: [fatal] rule rule__Abs__Group__3__Impl has non-LL(*) decision due to recursive rule invocations reachable from alts 1,2. Resolve by left-factoring or using syntactic predicates or using backtrack=true option.
warning(200): ../example.ui/src-gen/org/xtext/example/mydsl/ui/contentassist/antlr/internal/InternalMyDsl.g:317:33: Decision can match input such as "RULE_ID" using multiple alternatives: 1, 2
As a result, alternative(s) 2 were disabled for that input
warning(200): ../example.ui/src-gen/org/xtext/example/mydsl/ui/contentassist/antlr/internal/InternalMyDsl.g:317:33: Decision can match input such as "'\\'" using multiple alternatives: 1, 2
As a result, alternative(s) 2 were disabled for that input

but i activate the backtricking

// The antlr parser generator fragment.
fragment = parser.antlr.XtextAntlrGeneratorFragment {
options = {
backtrack = true
}
}

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Re: backtracking problem while generate grammar [message #730980 is a reply to message #730963]

Thu, 29 September 2011 16:17

Christian Dietrich

Messages: 14665
Registered: July 2009

Senior Member

Hi,

you could enable backtracking in parser.antlr.XtextAntlrUiGeneratorFragment too.
but it would be better to left-factor the grammar or using semantic predicates.

Term : Var | Abs | App;
Var : name = ID;
Abs : '\\' name = ID'.'(=>termList +=Term)+ ;
App : '(' t1 = Term t2 =Term ')';

~Christian

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

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Re: backtracking problem while generate grammar [message #731180 is a reply to message #730980]

Fri, 30 September 2011 08:04

samir

Messages: 27
Registered: September 2011

Junior Member

thanx christian

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Re: backtracking problem while generate grammar [message #731205 is a reply to message #731180]

Fri, 30 September 2011 09:08

samir

Messages: 27
Registered: September 2011

Junior Member

hello christian
but if I want to activate the backtrack, what I need to change, not enough to activate it from GenerateMyDsl.mwe2

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Re: backtracking problem while generate grammar [message #731208 is a reply to message #731205]

Fri, 30 September 2011 09:12

Christian Dietrich

Messages: 14665
Registered: July 2009

Senior Member

Hi,

dont understand your question. i wrote in my prev post what to do:

...
fragment = parser.antlr.XtextAntlrGeneratorFragment {
              options = {
                  backtrack = true
              }
            }
...
fragment = parser.antlr.XtextAntlrUiGeneratorFragment {
            	options = {
                  backtrack = true
              }
            }
...

~Christian

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

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Re: backtracking problem while generate grammar [message #731971 is a reply to message #731208]

Mon, 03 October 2011 15:10

samir

Messages: 27
Registered: September 2011

Junior Member

hello guys
sorry if I write again, now I solved the problem of left recursion, but when I run the application and create a new file.mydsl, the program gives me this exception

grammer:

Term : Var | Abs | App;
Var : name = ID;
Abs : '\\('param = ID ').'body = ID;
App : '('t1 = Term ')' t2 = Term;

0 [Worker-4] ERROR org.xtext.example.mydsl.ui.MyDslExecutableExtensionFactory - java.lang.NullPointerException
47 [Worker-4] ERROR org.eclipse.xtext.internal.ResourceServiceProviderDescriptor - null ExtensionFactory: org.xtext.example.mydsl.ui.MyDslExecutableExtensionFactory
org.eclipse.core.runtime.CoreException: null ExtensionFactory: org.xtext.example.mydsl.ui.MyDslExecutableExtensionFactory
at org.eclipse.xtext.ui.guice.AbstractGuiceAwareExecutableExtensionFactory.create(AbstractGuiceAwareExecutableExtensionFactory.java:57)
at org.eclipse.core.internal.registry.ConfigurationElement.createExecutableExtension(ConfigurationElement.java:262)
at org.eclipse.core.internal.registry.ConfigurationElementHandle.createExecutableExtension(ConfigurationElementHandle.java:51)
at org.eclipse.xtext.internal.ResourceServiceProviderDescriptor.get(ResourceServiceProviderDescriptor.java:40)
at org.eclipse.xtext.internal.ResourceServiceProviderDescriptor.get(ResourceServiceProviderDescriptor.java:1)
at org.eclipse.xtext.resource.impl.ResourceServiceProviderRegistryImpl$InternalData.getServiceProvider(ResourceServiceProviderRegistryImpl.java:40)
at org.eclipse.xtext.resource.impl.ResourceServiceProviderRegistryImpl.getResourceServiceProvider(ResourceServiceProviderRegistryImpl.java:75)
at org.eclipse.xtext.resource.impl.ResourceServiceProviderRegistryImpl.getResourceServiceProvider(ResourceServiceProviderRegistryImpl.java:91)
at org.eclipse.xtext.ui.resource.UriValidator.isValid(UriValidator.java:27)
at org.eclipse.xtext.ui.resource.Storage2UriMapperImpl.isValidUri(Storage2UriMapperImpl.java:99)
at org.eclipse.xtext.ui.resource.Storage2UriMapperImpl.getUri(Storage2UriMapperImpl.java:83)
at org.eclipse.xtext.builder.impl.ToBeBuiltComputer.getUri(ToBeBuiltComputer.java:154)
at org.eclipse.xtext.builder.impl.ToBeBuiltComputer.updateStorage(ToBeBuiltComputer.java:121)
at org.eclipse.xtext.builder.impl.XtextBuilder$2.visit(XtextBuilder.java:131)
at org.eclipse.core.internal.events.ResourceDelta.accept(ResourceDelta.java:68)
at org.eclipse.core.internal.events.ResourceDelta.accept(ResourceDelta.java:79)
at org.eclipse.core.internal.events.ResourceDelta.accept(ResourceDelta.java:79)
at org.eclipse.core.internal.events.ResourceDelta.accept(ResourceDelta.java:48)
at org.eclipse.xtext.builder.impl.XtextBuilder.incrementalBuild(XtextBuilder.java:137)
at org.eclipse.xtext.builder.impl.XtextBuilder.build(XtextBuilder.java:91)
at org.eclipse.core.internal.events.BuildManager$2.run(BuildManager.java:627)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:170)
at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:201)
at org.eclipse.core.internal.events.BuildManager$1.run(BuildManager.java:253)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
at org.eclipse.core.internal.events.BuildManager.basicBuild(BuildManager.java:256)
at org.eclipse.core.internal.events.BuildManager.basicBuildLoop(BuildManager.java:309)
at org.eclipse.core.internal.events.BuildManager.build(BuildManager.java:341)
at org.eclipse.core.internal.events.AutoBuildJob.doBuild(AutoBuildJob.java:140)
at org.eclipse.core.internal.events.AutoBuildJob.run(AutoBuildJob.java:238)
at org.eclipse.core.internal.jobs.Worker.run(Worker.java:55)
Caused by: java.lang.NullPointerException
at org.eclipse.xtext.ui.guice.AbstractGuiceAwareExecutableExtensionFactory.create(AbstractGuiceAwareExecutableExtensionFactory.java:50)
... 31 more

[Updated on: Mon, 03 October 2011 15:19]

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Re: backtracking problem while generate grammar [message #731974 is a reply to message #731971]

Mon, 03 October 2011 15:20

Christian Dietrich

Messages: 14665
Registered: July 2009

Senior Member

Hi,

looks very strange.
have you more stracktrace? did you do any changes to the generated code? why does getInjector return null in your case? did you try to debug into the code? are there any other error messages in the console?

~Christian

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

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