Re: What is correct way to describe this in BNF for an LL(1) parser

On 2 Nov 2005 22:13:51 -0500, don wrote:


> I can do everything I've needed to so far except for the absolute value
> function (eg | expression |). The problem is that the expression can
> expand back to this definition and, as it is simply stated now, the
> parser does not appear to tell the difference between closing '|' and
> the start of a nested expression. If I change the trailing "|" to
> something like '@' then the whole thing works OK.


That should not be the reason, as long as no expression can be empty or
contain | as an operand or operator (unary, dyadic, postfix).


> BTW, I also have the more standard " ABS ( expression ) " version and
> that gets me by for now, but I really would like the |...| notation as
> well.


I written several parsers with |x| for abs and so far experienced no any
problems. I'm using a different technique, though.


--
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de

Return to the comp.compilers page.
Search the comp.compilers archives again.