[antlr-interest] Re: syn pred / lookahaed doesn't work

[Gunnar Wagenknecht]

--- In antlr-interest at yahoogroups.com, "cintyram" <cintyram at y...> 
wrote:

> from what you have given i assume the follwoing :
> 1. a compilation unit is a statement list followed by zero or more
> functions 
> 2. a statementlist is a list of zero or more statements
> 3. and a statement is a variable declaration or "exit" or something
> else ..

That is right. The functions are function declarations. All 
statements before the first function declaration belongs to a non-
declared "main" function and all statements after a function 
declaration belongs to the declared function.
 

> in this case it is clear that for a look ahead of 1, ie  at k=1 ,

That's why I configured a lookahead of "k=2".

> also  i am asking out of personal suspicion did you have an alt 
which
> means that a statement rule can match a function also?
> like
>   statement : other alts
>                | function    /// do you have this in your grammar?
>                | other alts 
>           ;

No, this is not allowed. A statement is not allowed to have a 
function declaration.
 
> however i suggest that you should post the actual predicates that 
you
> used, to know why they dont seem to work ;

I tried LA in the statement rule to ensure a variable declaration is 
only matched if (("static"|"public"|...) IDENTIFIER) is found. But 
the generated parser ignores this completly.

The parser only contains a switch-case block in the statement rule 
similar to:

switch(LA(1))
{
...
case LITERAL_static:
   variableDeclaration();

...
}

So any "static" causes the parser to matched asvariable declaration. 
It doesn't care about a "function" or IDENTIFIER after this.

Cu, Gunnar




 

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