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

[Sven Efftinge <sven.efftinge@xxxxxxxxx>]

Hi Henrik,

one left recursion is in TerminalArithmeticExpression which can be a 
BinaryArithmenticExpression which can again be a 
TerminalArithmeticExpression etc.
Note that in LL grammars (i.e. those that don't like left recursion) one 
also defines the precedence of operators using the left factoring.

This is a typical example of how one creates non-left recursive 
mathmatical expressions, for instance:

Add :
  Multi ('+' Multi)*;

Multi :
  Primary ('*' Primary)*;

Primary :
  NUMBER |
  '(' Add ')';


Hope that helps,
Sven


> TerminalArithmeticExpression returns LogicExpression:           var=ID
>        | number=INT
>        | BinaryArithmeticExpression
>        | UnaryArithmeticExpression        | '(' 
> TerminalArithmeticExpression ')'
>        ;
>
> BinaryArithmeticExpression:
>     expression=TerminalArithmeticExpression ({Operation.left=current} 
> op=ArithmeticBinOperator)?;
>   
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