Re: Emulating advanced regex features using Lua patterns and pure Lua code

[Lorenzo Donati <lorenzodonatibz@...>]

On 20/06/2011 14.13, David Kastrup wrote:
> steve donovan<steve.j.donovan@gmail.com>  writes:
>
> > On Mon, Jun 20, 2011 at 12:12 PM, Lorenzo Donati
> > <lorenzodonatibz@interfree.it>  wrote:
> > > if pcre.match( haystack, "^foo|bar$" ) then ...
> > > may be rewritten in pure Lua as:
> > > if haystack:match "^foo$" or haystack:match "^bar$" then ...
> >
> > Ah, but soon as you get multiple alternation, especially nested, then
> > the resulting code is not so obvious. And obviously it is going to be
> > slower than any regexp implementation. OK, that may be acceptable for
> > the application, but the code generation could get hairy fast.
> >
> > Another idea is to use LPeg to implement a regexp subset - that should
> > be fast. But it does require non-triivial knowledge of LPeg which I
> > understand is not on your immediate to-do list ;)
>
> <URL:http://www.inf.puc-rio.br/~roberto/lpeg/re.html>

I know that, but: 1) it has LPeg as external dependency and 2) even if 
that dependency is acceptable, it has an unusual syntax, which (IIRC) 
moreover doesn't completely abstract over the underlying LPeg features, 
so you need to understand LPeg to a certain extent to use re's more 
advanced features.