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extraneous input '}' expecting EOF [message #892688]

Fri, 29 June 2012 08:46

Andrew A

Messages: 9
Registered: June 2012

Junior Member

I have a simple template language grammar:

grammar org.xtext.example.mydsl.MyDsl with org.eclipse.xtext.common.Terminals

generate myDsl "url here"

Model:
	statements+=Statement*;
	
Statement: (Text | Var);

Var :  '${' name=ID '}';
	
Text: v=(ID | ANY_OTHER );

When I tried to create test.dsl file:

test ${megavar} !@#$%^
testing{}

Eclipse underlines the last "}" with the error message "extraneous input '}' expecting EOF".

I don't understand why. Could you explain this point, please?

[Updated on: Fri, 29 June 2012 08:46]

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Re: extraneous input '}' expecting EOF [message #892696 is a reply to message #892688]

Fri, 29 June 2012 09:18

Alexander Nittka

Messages: 1193
Registered: July 2009

Senior Member

Hi,

'}' is a keyword in your grammar and hence is not covered by ANY_OTHER.

Text: v=(ID| ANY_OTHER| '}');

Alex

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Re: extraneous input '}' expecting EOF [message #892699 is a reply to message #892688]

Fri, 29 June 2012 09:22

Vlad Dumitrescu

Messages: 431
Registered: July 2009
Location: Gothenburg

Senior Member

Hi!

ANY_OTHER is tricky. It means "any other character not mentioned anywhere else", but '}' is not such a character, it is already a grammar symbol.

If you change the definition of Var to end with '}$' (for example), you will see it works.

In practice, you don't really want to use ANY_OTHER except in special cases. Instead, specify the range of accepted characters. It may be longer to write, but it's more resilient to change.

regards,
Vlad

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Re: extraneous input '}' expecting EOF [message #892860 is a reply to message #892699]

Sat, 30 June 2012 16:28

Andrew A

Messages: 9
Registered: June 2012

Junior Member

Thanks, Alexander and Vlad.

this works:

Text: v=(ID| ANY_OTHER| '}');

but this don't:

Model:
	statements+=Statement*;

Statement: Var | Text | WsText ;

Text: val=(PUNCTUATION|IDENT);
	
Var: '${' name=IDENT '}';

WsText: val=WS;
	
terminal IDENT: ('a'..'z'|'A'..'Z'|'_') ('a'..'z'|'A'..'Z'|'_'|'0'..'9')*;

terminal WS: (' ' | '\r' | '\n' | '\t')+;

terminal PUNCTUATION: ('(' | ')' | '.' | ',' | '=' | '{' | '}' | '*' | ';' | '+' | '-')*;

Should I update my Text rule every time I change keywords?

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Re: extraneous input '}' expecting EOF [message #892864 is a reply to message #892860]

Sat, 30 June 2012 19:00

Alexander Nittka

Messages: 1193
Registered: July 2009

Senior Member

Hi,

you have overlapping definitions. '}' is covered by the keyword in the Var-rule and the terminal Punctuation rule. The lexer will produce exactly one token (the keyword) which you do not allow in in the Text-rule.

The simplest way could be to make PUNCTUATION a datatype rule instead of a terminal rule.

Punctuation: ('(' | ')' | '.' | ',' | '=' | '{' | '}' | '*' | ';' | '+' | '-')+;

In this case the single elements will be tokenized as sequence of single keywords rather than as single punctuation token.

Alex

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