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Tue, 18 December 2018 03:55

Eclipse User

Hi,

I have a code written in ANTLR4 grammar which I need to convert to Xtext. I have converted a part of it and the below part gives an error: -

offline_expression
   : offline_or_expression
   ;

offline_or_expression
   : offline_and_expression ( 'or' offline_and_expression=offline_and_expression )*
   ;

offline_and_expression
   : offline_equals_expression ( 'and' offline_equals_expression=offline_equals_expression )*
   ;

offline_equals_expression
   : offline_not_equals_expression ( '=' offline_not_equals_expression=offline_not_equals_expression )*
   ;

offline_not_equals_expression
   : offline_greater_expression ( '!=' offline_greater_expression=offline_greater_expression )*
   ;

offline_greater_expression
   : offline_less_than_equals_expression ( '>' offline_less_than_equals_expression=offline_less_than_equals_expression )*
   ;

offline_less_than_equals_expression
   : offline_greater_equals_expression ( '<=' offline_greater_equals_expression=offline_greater_equals_expression )*
   ;

offline_greater_equals_expression
   : offline_less_than_expression ( '>=' offline_less_than_expression=offline_less_than_expression )*
   ;

offline_less_than_expression
   : offline_subtraction_expression ( '<' offline_subtraction_expression=offline_subtraction_expression )*
   ;

offline_subtraction_expression
   : offline_addition_expression ( '-' offline_addition_expression=offline_addition_expression )*
   ;

offline_addition_expression
   : offline_multiplication_expression ( '+' offline_multiplication_expression=offline_multiplication_expression )*
   ;

offline_multiplication_expression
   : offline_division_expression ( '*' offline_division_expression=offline_division_expression )*
   ;

offline_division_expression
   : offline_mod_expression ( '/' offline_mod_expression=offline_mod_expression)*
   ;

offline_mod_expression
   : offline_in_expression ( '%' offline_in_expression=offline_in_expression )*
   ;

offline_in_expression
   : ( offline_not_expression ( 'in' offline_not_expression=offline_not_expression )* )
   ;

offline_not_expression
   : ( '!' )? offline_boolean_expression
   ;

offline_boolean_expression
   : ( offline_method_call_expression | ( 'true' | 'false' ) )
   ;

offline_method_call_expression
   : ( offline_expression_atom | ( offline_method_call_expression_referenced_name ( '(' ')' | '(' offline_expression=offline_expression ( ',' offline_expression2=offline_expression )* ')' )* ) )
   ;

offline_method_call_expression_referenced_name
   : ( 'record' '.' )? ( identifier | CAMELCASE_IDENTIFIER ) ( '.' ( identifier | CAMELCASE_IDENTIFIER ) )*
   ;

offline_expression_atom
   : ( '(' offline_expression ( ',' offline_expression=offline_expression )* ')' | ( '-' )? INTEGER | ( '-' )? DECIMAL | STRING | offline_expression_atom_reference_name | 'null' )
   ;

offline_expression_atom_reference_name
   : ( 'record' '.' )? ( identifier | CAMELCASE_IDENTIFIER ) ( '.' ( identifier | CAMELCASE_IDENTIFIER ) )*
   ;

All the rule names in this code are underlined in red except 'offline_expression_atom_reference_name' and 'offline_method_call_expression_referenced_name'.
The error states "A class may not be a super type of itself".

Could anyone please explain why this is happening and how to overcome this error?
Regards!

Re: Error in Rules [message #1799970 is a reply to message #1799969]

Tue, 18 December 2018 03:57

Eclipse User

read here on how to write a expression grammar: https://typefox.io/parsing-expressions-with-xtext https://www.eclipse.org/Xtext/documentation/307_special_languages.html#expressions

Re: Error in Rules [message #1799973 is a reply to message #1799970]

Tue, 18 December 2018 04:18

Eclipse User

See also here https://speakerdeck.com/kthoms/introduction-to-expression-languages-with-xtext
And "Implementing Domain-Specific Languages with Xtext and Xtend " from Lorenzo Bettini.

Re: Error in Rules [message #1799982 is a reply to message #1799973]

Tue, 18 December 2018 05:20

Eclipse User

Thank You Christian and Karsten! I will refer these documents.

Re: Error in Rules [message #1800037 is a reply to message #1799982]

Wed, 19 December 2018 04:33

Eclipse User

Hi,

As a side question, does it take a long time to generate artifacts of a considerably long xtext grammar file (1236 lines of code)? I started generating artifacts but now it's been about 6 hours and it is still not done. I do not understand whether it is working properly or not.

Regards!

Re: Error in Rules [message #1800044 is a reply to message #1800037]

Wed, 19 December 2018 05:28

Eclipse User

it should never take 6 hours. if so there might be somthing strange with your grammar or you ran into a bug

Re: Error in Rules [message #1800045 is a reply to message #1800037]

Wed, 19 December 2018 05:28

Eclipse User

Depends on the grammar complexity (not size) and heap. I never had a grammar compiling that long, not even close to that. I would consider everything above 1 min already as really long.

Please understand that we can't give detailed answers without knowing internals of the project. Usually customers that we serve directly and where we are involved into the language development can be helped much better than we can here in the forum.

Re: Error in Rules [message #1800302 is a reply to message #1800045]

Sun, 23 December 2018 22:59

Eclipse User

Hi,
I have the below rule in my grammar,

QUESTION_LINE_COMMENT
   : ( '//?' ~('\r'|'\n')* )  
 
   ;

I get an error as given in the image I have attached.
Could you please tell why this error occurs, and if possible, how to eliminate it?
Regards!

Attachment: ~error.png
(Size: 5.65KB, Downloaded 144 times)

Re: Error in Rules [message #1800307 is a reply to message #1800302]

Mon, 24 December 2018 02:06

Eclipse User

Hi

Did you mean ! as in

terminal SL_COMMENT:
'--' !('\n' | '\r')* ('\r'? '\n')?;

Regards

Ed Willink

Re: Error in Rules [message #1800311 is a reply to message #1800307]

Mon, 24 December 2018 03:32

Eclipse User

Yes, it worked. Thank you very much!

I have another question, if you wouldn't mind.

My Grammar looks like below: -

Model:
	(test+=Test)*
;

//OfflineExpressionParser

Test:
	Comment | Exp | MainExp 
;

Comment:
	comment=COM
;
Exp:
	exp='Hello'
;

MainExp:
	'start' '{' (Exp=Exp)+ '}'
;

terminal COM:
	( '---' ('-')+ (' ') (('A'..'Z'|'0'..'9')+ (' '))+ ('-')+ )
;

Now, when I try the 'Comment' rule in the runtime, the resulting responses are given in the attached image.

Could you please tell me the reason for the Comments to be recognized/not recognized by the program at different instances?
I tried modifying the grammar as below, but it gave the same results: -

Model:
	(test+=Test)*
;

Test:
	Comment | Exp | MainExp 
;

Comment:
	comment=COM
;
Exp:
	exp='Hello'
;

MainExp:
	Comment | ('start' '{' (Exp=Exp)+ '}')
;

terminal COM:
	( '---' ('-')+ (' ') (('A'..'Z'|'0'..'9')+ (' '))+ ('-')+ )
;

What if I wanted for the program to recognize Comments anywhere in the file? Could you please tell me how I could modify the grammar?
Regards!

Attachment: commentError.png
(Size: 8.95KB, Downloaded 138 times)

[Updated on: Mon, 24 December 2018 03:33] by Moderator

Re: Error in Rules [message #1800329 is a reply to message #1800311]

Mon, 24 December 2018 11:35

Eclipse User

Hi

Your grammar does not allow comments in Exps.

Regards

Ed Willink

Re: Error in Rules [message #1800337 is a reply to message #1800311]

Mon, 24 December 2018 16:13

Eclipse User

P J wrote on Mon, 24 December 2018 03:32

What if I wanted for the program to recognize Comments anywhere in the file? Could you please tell me how I could modify the grammar?!

The easiest way to have comments anywhere is to hide them just like whitespace. e.g

grammar org.eclipse.ocl.xtext.base.Base hidden(WS, ML_COMMENT, SL_COMMENT) //with org.eclipse.xtext.common.Terminals

The hidden comments are recoverable from the leaf nodes of an Xtext Node element.

Regards

Ed Willink

Re: Error in Rules [message #1800370 is a reply to message #1800337]

Wed, 26 December 2018 00:36

Eclipse User

Thank You Ed! Hiding the Comments worked for me. :-)

Re: Error in Rules [message #1800503 is a reply to message #1800370]

Mon, 31 December 2018 00:58

Eclipse User

Hi,
I have the below rule in the antlr4 grammar that I'm converting to xtext: -

copy_on_crud_default_to
   : dataitem_reference ( ( ',' dataitem_reference )+ )?
   ;

I get a warning for the optional symbol (?) at the end stating "More than one cardinality was set. Merging '?' with previously assigned cardinality to '*'."
I know the error is because the two cardinalities give different meanings.
Does the above rule convey a non-greedy operator?

Could you please tell me how I should convert this correctly to xtext?

Re: Error in Rules [message #1800506 is a reply to message #1800503]

Mon, 31 December 2018 02:01

Eclipse User

You should use assignments and assign to lists

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