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Xtext [message #886434]

Thu, 14 June 2012 19:17

Ajit Rathore
Messages: 1
Registered: June 2012

Junior Member

I know it has been discussed many times but I could not resolve it on my own hence the post:

I get the message "The rule 'LSParameter' is left recursive." and "This rule call is part of a left recursive call graph." on the grammer below:

Grammer Snippet:

ArithMathicStatement returns LSParameter:
{ArithMathicStatement}
(left=LSParameter operator+=ArithmeticOperator right=LSParameter)
;

BigArithmatic:
left1=ArithMathicStatement (operatorb+=ArithmeticOperator right1+=LSParameter)*
;

LSParameter returns LSParameter:
(LSBoolean | LSNullLiteral | LSIntLiteral | LSStringLiteral | LSConstCall|LSNothingLiteral|LSFunctionCall|BigArithmatic | LSPropertyCall )
;

Please let me know if more information is needed.

[Updated on: Thu, 14 June 2012 19:30]

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Re: Xtext [message #886453 is a reply to message #886434]

Thu, 14 June 2012 20:39

Henrik Lindberg
Messages: 2427
Registered: July 2009

Senior Member

On 2012-15-06 1:17, Ajit Rathore wrote:
> I know it has been discussed many times but I could not resolve it on my
> own hence the post:
>
> I get the message "The rule 'LSParameter' is left recursive." on the
> grammer below:
>
> Grammer Snippet:
>
> ArithMathicStatement returns LSParameter:
> {ArithMathicStatement}
> (left=LSParameter operator+=ArithmeticOperator right=LSParameter)
> ;
>
> BigArithmatic:
> left1=ArithMathicStatement (operatorb+=ArithmeticOperator
> right1+=LSParameter)* ;
>
> LSParameter returns LSParameter:
> (LSBoolean | LSNullLiteral | LSIntLiteral | LSStringLiteral |
> LSConstCall|LSNothingLiteral|LSFunctionCall|BigArithmatic |
> LSPropertyCall )
> ;
>
>
There is a formula to follow for expressions - your snippet does not
follow that forumla. Try googling for "Xtext expression left recursion"
and you will find blog posts by Meinte Boersma and Sven Efftinge on the
topic.

There is also an example Expression language.

Then look at other more complex languages.

Regards
- henrik

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Re: Xtext [message #891689 is a reply to message #886453]

Mon, 25 June 2012 09:52

Lorenzo Bettini
Messages: 1117
Registered: July 2009

Senior Member

On 06/15/2012 02:39 AM, Henrik Lindberg wrote:
> On 2012-15-06 1:17, Ajit Rathore wrote:
>> I know it has been discussed many times but I could not resolve it on my
>> own hence the post:
>>
>> I get the message "The rule 'LSParameter' is left recursive." on the
>> grammer below:
>>
>> Grammer Snippet:
>>
>> ArithMathicStatement returns LSParameter:
>> {ArithMathicStatement}
>> (left=LSParameter operator+=ArithmeticOperator
>> right=LSParameter)
>> ;
>>
>> BigArithmatic:
>> left1=ArithMathicStatement (operatorb+=ArithmeticOperator
>> right1+=LSParameter)* ;
>>
>> LSParameter returns LSParameter:
>> (LSBoolean | LSNullLiteral | LSIntLiteral | LSStringLiteral |
>> LSConstCall|LSNothingLiteral|LSFunctionCall|BigArithmatic |
>> LSPropertyCall )
>> ;
>>
>>
> There is a formula to follow for expressions - your snippet does not
> follow that forumla. Try googling for "Xtext expression left recursion"
> and you will find blog posts by Meinte Boersma and Sven Efftinge on the
> topic.
>
> There is also an example Expression language.

This is an example of Expression language

http://xsemantics.sourceforge.net/xsemantics-documentation/Expressions-example.html#Expressions

hope it helps

cheers
Lorenzo

--
Lorenzo Bettini, PhD in Computer Science, DI, Univ. Torino
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