Re: [boost] [Review] xpressive

From: Eric Niebler (eric_at_[hidden])
Date: 2005-09-15 00:59:47

Christopher Kohlhoff wrote:
> Hi Eric, Scott,
> 
> Sorry if this is getting a bit off-topic for the xpressive review...
> 

Mmm, drifting a bit, perhaps, but it's worth clearing this up.

> I'm not totally familiar with the xpressive API, but as far as I
> understand the regex APIs (even with iterators) are not sufficient for
> clean integration with async I/O.
> 
> What you need is a stateful decoder that you can feed data to as you
> receive it off the wire, and it tells you when it is done, or when it
> needs you to feed it more data.
> 

What you are describing, at least in regex terms, is a partial match. 
Ordinarily, a regex match will give you a "yes" or a "no" answer. With a 
partial match, you can get a "maybe" if the input sequence is exhausted 
before the regex state machine has reached its final state. Boost.Regex 
and xpressive both support partial matches via the match_partial switch, 
which is documented (for Boost.Regex) here:

http://boost.org/libs/regex/doc/partial_matches.html

Note that TR1 regex does not support partial matches, for the simple 
reason that we weren't able to come up with satisfactory standardese in 
time.

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