[boost] Re: Announcing: xpressive

From: Eric Niebler (eric_at_[hidden])
Date: 2003-11-18 11:50:10

Brock Peabody wrote:
> 
> Maybe this is a silly question, but do we need Regular Expressions now that
> we have Spirit?  I've never used regular expressions before so I may be
> missing something, but the syntax is frightening compared to EBNF.  Could
> the dynamic syntax be EBNF too?

As a wise man once said, don't yuck my yum. :-) REs are used in dynamic 
contexts: text editors, log file parsers, URL rewriters, etc., and there 
needs to be some facility in C++ for supporting that syntax. But most 
REs are statically hard-coded. Since all the RE machinery is there to 
support dynamic REs, it should be possible to reuse it statically to 
give the hard-coded REs more power and better performance.

As I mentioned earlier in the thread, in xpressive parsers are merely 
regex factories. It would be possible to write a parser to convert 
strings of EBNF into a regex at runtime and execute it. Then you have 
the runtime equivalent of Spirit. Heck, you could write a parser to turn 
your grocery list into a regex if you really want to. :-)

-- 
Eric Niebler
Boost Consulting
www.boost-consulting.com