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Xtext grammar [message #1731328]

Wed, 04 May 2016 10:43

RamaRao Nandamuri

Messages: 120
Registered: April 2016

Senior Member

Hi,

I have syntax like

def a, a[10](10), a(10)[10], a{10}[10](10), a(10)[10){10}, a[10]{10}(10)

No guarantee of order of declaration for [10] or {10} or (10).

I have written grammar like this

Decl : 'def' name+=ID
(isArray?='[' (maxOccurs+=NUMBER) ']')?
(isRange?='[' (range+=RANGE) ']')?
(isChar?='[' (Id+=ID) ']')?
(hasSize ?= '(' varsize=NUMBER ')')?
('=' Id+=ID ('(' Id+=ID (','? Id+=ID)* ')')?)?
('=' const=Constant)?
('=' string=STRING)? ','?
;

I know here my grammar follows the order of definition. How can I handle this which allows me all the orders?

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Re: Xtext grammar [message #1731329 is a reply to message #1731328]

Wed, 04 May 2016 10:49

Christian Dietrich

Messages: 13181
Registered: July 2009

Senior Member

have a look at the grammar concept of unordered groups

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Re: Xtext grammar [message #1731331 is a reply to message #1731329]

Wed, 04 May 2016 11:19

RamaRao Nandamuri

Messages: 120
Registered: April 2016

Senior Member

Thank you. I got the solution. The main problem for me is questioning google about my problem

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Re: Xtext grammar [message #1731444 is a reply to message #1731331]

Thu, 05 May 2016 10:33

RamaRao Nandamuri

Messages: 120
Registered: April 2016

Senior Member

Hi Christian,

My below grammar is failing because keyword 'math' is optional

Assignment returns Statement : (name=('math')? ((exp+=Expression) (','? exp+=Expression)*)|((oneDecl+=OneDecl) (','? oneDecl+=OneDecl)*)) ','?;

But if I remove 'math' optional it is working:

Assignment returns Statement : (name=('math') ((exp+=Expression) (','? exp+=Expression)*)|((oneDecl+=OneDecl) (','? oneDecl+=OneDecl)*)) ','?;

But I want case 1. Could you please tell me how can I achieve that?

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Re: Xtext grammar [message #1731446 is a reply to message #1731444]

Thu, 05 May 2016 10:48

Christian Dietrich

Messages: 13181
Registered: July 2009

Senior Member

Please share the complete grammar

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Re: Xtext grammar [message #1731522 is a reply to message #1731446]

Fri, 06 May 2016 12:47

RamaRao Nandamuri

Messages: 120
Registered: April 2016

Senior Member

Model:
(variables+=Variable)*
;

Variable:
name=ID '=' expression=Expression
;

Expression:
BooleanExpression;

BooleanExpression returns Expression:
Comparison
(({AndOrExpression.left=current} op=("||"|"&&")) right=Comparison)*;

Comparison returns Expression:
Equals
(({Comparison.left=current} op=("<") ) right=Equals)*;

Equals returns Expression:
Addition
(({Equals.left=current} op=("==") ) right=Addition)*;

Addition returns Expression:
Multiplication
(({Plus.left=current} '+' | {Minus.left=current} '-')
right=Multiplication)*;

Multiplication returns Expression:
Prefixed (({MultiOrDiv.left=current} op=("*"|"/")) right=Prefixed)*;

Prefixed returns Expression:
{BooleanNegation} =>"!" expression=Atomic | /* right associativity */
{ArithmeticSigned} =>"-" expression=Atomic | /* right associativity */
Atomic;

Atomic returns Expression:
'(' Expression ')' |
{NumberLiteral} value=INT |
{StringLiteral} value=STRING |
{BooleanLiteral} value=('true'|'false') |
{VariableReference} ref=[Variable]
;

// the types will be used only internally by the type system
Type:
{IntType} 'int' |
{StringType} 'string' |
{BooleanType} 'boolean'
;

[Updated on: Fri, 06 May 2016 13:38]

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Re: Xtext grammar [message #1731523 is a reply to message #1731522]

Fri, 06 May 2016 12:49

RamaRao Nandamuri

Messages: 120
Registered: April 2016

Senior Member

No Message Body

[Updated on: Sat, 07 May 2016 11:36]

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Re: Xtext grammar [message #1731526 is a reply to message #1731523]

Fri, 06 May 2016 13:29

Christian Dietrich

Messages: 13181
Registered: July 2009

Senior Member

well i had hoped for a minimal reproducable example not 200 lines of grammar.

the there is a question you have to answer: a assignment can start with a assignment?

Assignment: ('math')? (expression+=Expression '=' expression+=Expression) (',' expression+=Expression'=' expression+=Expression)*;

Expression:
Primary
;

Primary returns Expression: value+=NUMBER |assignment+=Assignment
;

i dont know if that is intended
thats the point of the left recusion.
what should happen here ?!?

and it makes no sense to me since this is already handled on assignmentlevel ?!?

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