Re: [Boost-users] Simple fast parsing

Subject: Re: [Boost-users] Simple fast parsing
From: Joel de Guzman (joel_at_[hidden])
Date: 2009-06-22 11:11:50

Alan M. Carroll wrote:
> At 05:49 PM 6/21/2009, you wrote:
>> Christopher Jefferson wrote:
>> 
>>> Looking at the documentation, Boost::Spirit seems like a very big
>>> hammer to crack this quite small nut, and it is unclear to me how
>>> well it would fit into an existing recursive decent parser. Has
>>> anyone ever used it as such? Is there a simple alternative?
>> Spirit is well tuned for small parsing tasks like this. It is a 
>> modular RD parser. What you need is what you pay for. The code is 
>> as tight as it can be.
> 
> I don't think this solves his problem. 

What is the problem? Speed, right? Then I don't see why it does
not solve the problem.

> Note that he got a 10X speed
> up by changing to a buffer with his existing parser, so the _parsing_
> code isn't the bottle neck.  It's better I/O that's needed. I suspect

And Spirit uses a better I/O through generic Forward Iterators.

> it's the locking done by streams on each operation, so he's basically
> doing a lock on every character. I think he'd be better off using the
> forward iterator idea and then either writing a small wrapper class
> on streams to block read or use the lower level read buffer
> interface.

I think you are under-estimating the complexity of writing a
humble number parser from a Forward Iterator. It's not as simple
as it looks and gets pretty hairy when you get past the toy
examples.

Regards,
-- 
Joel de Guzman
http://www.boostpro.com
http://spirit.sf.net