RE: is P::RD LL(1) LL(N) LR(1) LR(N) ?

> From: Damian Conway [mailto:[email protected]] Sent: 2002/03/21 00:19
> Yves wrote:
> 
> A really excellent summary of the various classes of parser 
> and why RecDescent
> doesn't quite fit in any of them. Thanks, Yves.

Cheers. And there I was expecting to get slammed for some subtlety. :-)

> 	When Parse::RecDescent encounters something like this 
> it should error
> 	(its documented that it will, but I haven't checked)...
> 
> It definitely does.

I assumed that it did.

> 
> 	...as it will go into an endless loop on the 'expr' 
> rule. Unfortunately 
> 	however TheDamian hasnt implemented multi level left 
> recursion checking...
> 
> Oh, yes he has! RecDescent does a complete graph traversal 
> looking for n-ary
> left-recursion loops and fails to compile the grammar if it finds any
> left-recursive loop involving any number of rules. It has 
> done this since its
> earliest versions.

Doh! My confusion comes from misremembering (really must learn to double
check _anything_ I think I remember) the following:
(from P::RD documentation)
More subtle forms of left recursion (for example, through the second item in
a rule after a ``zero'' match of a preceding ``zero-or-more'' repetition, or
after a match of a subrule with an empty production) are not found. 

Apologies, and Ill update the node as well.

Cheers,
Yves