[news.eclipse.modeling.tmf] Re: Removing left recursion...

[Henrik J <hjoensson@xxxxxxxxx>]

Thanks for the tips! I managed to get a bit further  :p 

I managed to come to the arithmetic expression part of the grammar. I tried to use your tips but I still got some left recursion that I can't remove.

Here's the full grammar:

grammar SvtObjSpec with org.eclipse.xtext.common.Terminals

generate svtObjSpec "http://SvtObjSpec";

Spec:
  '#definitions'
  (definitions+=Definition ';')*
  '#assumptions'
  (assumptions+=LogicExpression ';')*
  '#requirements'
  (requirements+=LogicExpression ';')*
  ;

Definition: 
   atom=ID
   expression=LogicExpression;

LogicExpression :
	  (TerminalBinaryExpression ({Operation.left=current} op=LogicBinOperator)?)
	| (TerminalArithmeticExpression ({Operation.left=current} op=CompareOperation)?)
	;

TerminalBinaryExpression returns LogicExpression:
	'(' LogicExpression ')'
	| atom=ID
	| "TRUE"
	| "FALSE"
	;

LogicBinOperator:  
         '&'
       | '#'
       | '->' 
       | '<->'
       | '<-'
       | '#!';

LogicUnOperator :   
         '~'
       | '@';

TerminalArithmeticExpression returns LogicExpression:  
         var=ID
       | number=INT
       | BinaryArithmeticExpression
       | UnaryArithmeticExpression 
       | '(' TerminalArithmeticExpression ')'
       ;

BinaryArithmeticExpression:
	expression=TerminalArithmeticExpression ({Operation.left=current} op=ArithmeticBinOperator)?;
     	
ArithmeticExpressionList : 
       expression=TerminalArithmeticExpression
       (',' expressionList=ArithmeticExpressionList)?; 

UnaryArithmeticExpression:
	op=ArithmeticUnOperator expression=TerminalArithmeticExpression;

MinMaxExpression:
       ('MIN' | 'MAX') '(' ArithmeticExpressionList ')';
       
ArithmeticBinOperator: 
         '+'
       | '-'
       | '*'
       | '/'
       | '%';

ArithmeticUnOperator: '-';


CompareOperation:   
         '<'
       | '<='
       | '>'
       | '>='
       | '<>'
       | '=';


And these are the errors I get:
error(210):  The following sets of rules are mutually left-recursive [ruleTerminalArithmeticExpression, ruleBinaryArithmeticExpression]
error(210):  The following sets of rules are mutually left-recursive [ruleTerminalArithmeticExpression, rule__BinaryArithmeticExpression__Group__0, rule__BinaryArithmeticExpression__ExpressionAssignment_0, rule__TerminalArithmeticExpression__Alternatives] and [ruleTerminalArithmeticExpression, ruleBinaryArithmeticExpression, rule__BinaryArithmeticExpression__Group__0, rule__BinaryArithmeticExpression__ExpressionAssignment_0, rule__TerminalArithmeticExpression__Alternatives]

I'm thankful for any tips!

Best regards
Henrik