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Overriding terminal StRING [message #542495]

Fri, 25 June 2010 02:01

Eclipse User

Hi,

I had to override the terminal rule STRING because in my grammar there's no string with line breaks in it allowed and also a '$' should be escape-able. So I defined the rules:

terminal STRING:
	'"' (STR_ESC | !('"'|'\r'|'\n'|'\\'))* '"'
	;
	
terminal STR_ESC:
	'\\'('b'|'t'|'n'|'f'|'r'|'"'|'\\'|'$')
	;

The line break thing works fine but an input

"foo\$bar"

evokes a syntax error "Illegal escape character \$"

Is there anything that I should configure in the parser?

- Alex

Re: Overriding terminal StRING [message #542507 is a reply to message #542495]

Fri, 25 June 2010 02:46

Eclipse User

Hi Alex,

if you override the terminal rule, you should consider to override the
value converter, too. Please refer to the documentation at
http://www.eclipse.org/Xtext/documentation/1_0_0/xtext.html# valueconverter
for details.

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

Am 25.06.10 08:01, schrieb Alex:
> Hi,
>
> I had to override the terminal rule STRING because in my grammar there's
> no string with line breaks in it allowed and also a '$' should be
> escape-able. So I defined the rules:
>
> terminal STRING:
> '"' (STR_ESC | !('"'|'\r'|'\n'|'\\'))* '"'
> ;
>
> terminal STR_ESC:
> '\\'('b'|'t'|'n'|'f'|'r'|'"'|'\\'|'$')
> ;
>
> The line break thing works fine but an input "foo\$bar" evokes a syntax
> error "Illegal escape character \$"
>
> Is there anything that I should configure in the parser?
> - Alex

Re: Overriding terminal StRING [message #542524 is a reply to message #542507]

Fri, 25 June 2010 04:19

Eclipse User

Thanks for that hint!

I now added a binding to the MyDslRuntimeModule and tried to implement a MyDslStringValueConverter.

	@Override
	public Class<? extends IValueConverterService> bindIValueConverterService() {
	  return MyDslStringValueConverter.class;
	}

import org.eclipse.xtext.conversion.IValueConverterService;
import org.eclipse.xtext.conversion.ValueConverterException;
import org.eclipse.xtext.parsetree.AbstractNode;

public class MyDslStringValueConverter implements IValueConverterService {

	@Override
	public Object toValue(String string, String lexerRule, AbstractNode node)
			throws ValueConverterException {
		// TODO Auto-generated method stub
		return null;
	}

	@Override
	public String toString(Object value, String lexerRule) {
		// TODO Auto-generated method stub
		return null;
	}
}

But where do I configure that my rule STRING should only return its value?

Do I now have to implement a value converter for each of my rules in the overridden method toValue() ?

I thought I could rather implement something like that:

public class MyDslStringValueConverter extends AbstractLexerBasedConverter<String> {

	@Override
	public String toValue(String string, AbstractNode node)
			throws ValueConverterException {
		return node.getElement().toString();
	}
}

But I don't know how to bind it...

[Updated on: Fri, 25 June 2010 04:25] by Moderator

Re: Overriding terminal StRING [message #542532 is a reply to message #542524]

Fri, 25 June 2010 04:38

Eclipse User

Extend the DefaultTerminalConverters (that class gives you an idea what
to do) and see how it is bound in the DefaultRuntimeModule.

Alex

Re: Overriding terminal STRING [message #542987 is a reply to message #542532]

Mon, 28 June 2010 02:51

Eclipse User

I did following:

public class MyDslRuntimeModule extends com.bosch.AbstractTpsRuntimeModule {

	@Override
	public Class<? extends org.eclipse.xtext.conversion.IValueConverterService> bindIValueConverterService() {
		return MyTerminalConverters.class;
	}
}

public class MyTerminalConverters extends DefaultTerminalConverters {
	
	
	public static class STRINGValueConverter extends AbstractValueConverter<String> {
		public String toString(String value) {
			if (value == null)
				throw new ValueConverterException("STRING-value may not be null.", null, null);
			return '"' + Strings.convertToJavaString(value, false) + '"';
		}

		public String toValue(String string, AbstractNode node) {
			if (string == null)
				return null;
			try {
				return string.substring(1,string.length()-1);	// return value of string (without '"')
			} catch (IllegalArgumentException e) {
				throw new ValueConverterException(e.getMessage(), node, e);
			}
		}
	}
	
	@Inject
	private org.eclipse.xtext.conversion.impl.STRINGValueConverter stringValueConverter;
	
	@ValueConverter(rule = "STRING")
	public IValueConverter<String> STRING() {
		return stringValueConverter;
	}
	
}

But nevertheless I get the parser error "illegal escape character \$" for a input a = "hello\$world"

the rules for Strings are

terminal STRING:
	'"' (STR_ESC | !('"'|'\r'|'\n'|'\\'))* '"'
	;
terminal STR_ESC:
	'\\'('b'|'t'|'n'|'f'|'r'|'"'|'\\'|'$')
	;

EDIT:
I forgot to change

	@Inject
	private org.eclipse.xtext.conversion.impl.STRINGValueConverter stringValueConverter;

to my own STRINGValueConverter

Sorry for that!

[Updated on: Mon, 28 June 2010 03:04] by Moderator

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