[antlr-interest] newbiew question on parsar grammar

Sebastian Kaliszewski sk at z.pl
Sun Dec 12 04:12:14 PST 2004


Dnia pią 10. grudzień 2004 17:44, John MccLain napisał:
> Howdy,
> Sebastian Kaliszewski replied to an earlier  post of mine (See original
> post below) stating that the parser was waiting
> for more input. He was correct - If I entered another NUM, the parser
> processed it and continued to wait again. He also mentioned that my
> startrule should have a check for EOF. I.E.:
> Your start rule should have have EOF checking in it.
> something like:
>
> expression: simpleexp ((LE|GE|NE|EQ|LT|GT) simpleexp )? EOF
>
> EOF checking is not implicit since many languages allow arbitrary
> garbage afterthe program.
>
> BUT, what is the rule for EOF,

The rule (token) for EOF is EOF. Exactly as i wrote.

> and will this cause the parser to stop busy
> waiting for input?

It should

> That is what I want to do. Right now I am using standard
> input (through the console in eclipse), but ultimately, I will be passing
> an expression or function
> string into the parser for it to build a parse tree. How would I gracefully
> exit the parser at the end of the input string ( or for now, standard in)

Just use that soecial EOF token. It's automatically generated byt the lexer 
when input terminates.


rgds
-- 
Sebastian Kaliszewski


 
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