From: Kaspar Schiess <eule@...>
Date: 2010-12-29T20:01:23+09:00
Subject: Re: [ANN] parslet 1.0 - a PEG parser library


> + Any performance benchmarks?

Official ones, no. Working with it: I just might have gotten the 
impression that there is room for improvement. (slow!) This is certainly 
the next thing on the menu. For example, it uses exceptions heavily 
which isn't the fastest thing to do. Can be and will be changed.

> + Does this PEG support left recursion?
Not yet. (Or only in the limited fashion, after a grammar 
transformation) Cool you mention the possibility to me, might just add 
that.

> + I assume with it subclassing Parslet::Parser that it does support language extension via further subclassing... But does that also imply that it can't support composition? I've usually seen that via multiple inheritance, and we'd usually do it via modules in ruby.
> 
> AH! I see that Parslet is a module and provides at least some of the grammar API.

That's a complicated topic ;) Parser rules are just methods on a class, 
so go ahead and use modules, classes and other tricks any way you like 
it. Like in example/ip_address.rb.

The documentation tries to simplify that for the general case. And I 
have yet to see a sample of composition that is really useful (in the 
sense of orthogonality of pieces).

Also, don't dig too hard, hidden features lurking to bite you ;)

regards,
kaspar