[antlr-interest] help

[Sinan]

Balvinder Singh wrote:
> 
> Hi...
> 
> I have a rule, which has 3 conflicts. plz help me to resolve it.
> 
> If I change it to context free grammar  and use some syntactic predicate,
> will be a right way or not.
> 
> parser rule
> picture_string : (currency)? ((picChar)+ (repeat)?)+ (Punctuation
> ((picChar)+ (repeat)?)+)*
> 
> currency and picChar is alphabet
> 
> repeat : "(" Integer ")"
>        ;
> 
> lexer rule
> Punctuation : ('/' | ',' | '.' | ':')
>             ;
> 
> so I have conflict in picture_string.
> 
> balvinder

If currency and picChar are alphabet with no distinguishing properties,
then obviously
no way to disambiguate exists.

However , othwerwise, you can always use


picture_string : ((currency)=>currency| ) ...

I wrote ( and posted ) a Fortran 77 parser at one time. Due to the free
form 
nature of the language, I had to only parse characters as tokens, and
made
everything else a parser rule. The problem with that approach is of
course, you don't
know what you've got until you parse the statement , and then re-parse
it ....

Wreaks havoc with error statements.

so basically you do

 statement:		(dostatement)=> dostatement
		|	(writestatement)=> writestatement
		...
		|	assignstatement
	;

Now when you run into a bad statement ( say a bad write statement)
e.g. "    write(6,7("
it will always say that you have a bad assignstatement.

sinan




sinan

 

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