Re: [mind game] Seeking for simple task impossible via regexps

["Soni L." <fakedme@...>]

On 24/02/17 03:18 PM, Coda Highland wrote:
> On Fri, Feb 24, 2017 at 9:18 AM, Roberto Ierusalimschy
> <roberto@inf.puc-rio.br> wrote:
> > > In layman's terms, this means that there are languages that LPeg can
> > > parse that PCRE cannot. (For example, PCRE cannot parse the balanced
> > > parentheses language without calling out to Perl code.)
> > PCRE (and the Perl engine) can parse the balanced parentheses
> > language. Check for "(?R)".
> >
> > -- Roberto
> Oh. Huh. I actually went and tried to research it before I posted
> that, and I hadn't found a solution using that technique. TIL, I
> guess! Though that's only supported by Perl, Ruby, and libpcre, not by
> other PCRE-style implementations like Javascript and Python.
>
> I don't know if there's a concrete answer to whether a regular
> language with recursion is as powerful as a nondeterministic pushdown
> automaton. My intuition says that they're equivalent to deterministic
> PDAs, which are known to be strictly weaker than NPDAs, but in terms
> of real-world parsing tasks I'm not certain if that ends up mattering.
>
> /s/ Adam

Can you parse HTML with LibPCRE?

I think that'd answer your question.

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