[news.eclipse.modeling.tmf] Re: Keywords vs. tokens

[Sven Efftinge <sven.efftinge@xxxxxxxxx>]

Hi Marco,

keywords have higher precedence than terminal rules, that is if you have 
a keyword 'foo' an input 'foo' will be lexed as the keyword not as an 
identifier. That is why we allow identifiers to be escaped like so 
'^foo' in order to resolve such conflicts.

Sven

Marco schrieb:
> Hi Sebastian,
>
> Thank you for the hint. I tried it but still keywords are recognized as 
> IDs.
>
> From_import :
> ____'from' FQN 'import' ('*' | ((FQN ('as' FQN)?) (',' FQN ('as' 
> FQN)?)*)) ;
>
> Foo_KW returns ecore::EString :
> ___'foo' | 'FOO' ;
>
> FQN :
> ____ID ('.' ID)* ;
>
> terminal ID : '^'?('a'..'z'|'A'..'Z'|'_') 
> ('a'..'z'|'A'..'Z'|'_'|'0'..'9')* ;
>
> I get an 'No viable alternative error' if the text intended to be FQN is 
> FOO.
>
> I do not understand why and how to work-around.
>
> The only chance I see is to split ID in ID_first_letter and 
> ID_trailing_letter, and write a data type rule to compose ID out of it. 
> But this not really concise.
>
> br
> m


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