RE: [boost] Re: Formal Review: The Spirit Parser Framework.

From: Thomas Wenisch (twenisch_at_[hidden])
Date: 2002-10-22 14:05:01

Hartmut,

On Tue, 22 Oct 2002, Hartmut Kaiser wrote:

> Peter Dimov wrote:
> 
> > > After what your code looks like:
> > >
> > >     nonctl_char = urange_p( '\x21', '\xFF' );
> >
> > The question is, would you ever want ['\x21', '\xFF'] to
> > _not_ be a valid
> > range?
> 
> If this is what you want, you could write 'epsilon_p - urange_p( '\x21',
> '\xFF' )', essentially this means 'match everything (epsilon_p) except
> ('-') the given range :-)
> 

Perhaps I misread Peter's post, but I understood his question to mean,
why is the assertion error useful?  Why would we want range_p to assert if
the lower bound > upper bound?  (Peter, correct me if I am misinterpreting
your question).

If this causes users headaches because of the signed-ness of char, why
not simply reverse the bounds, since this almost certainly what was
intended.  Here, I think it would be better for the code to simply work,
instead of issuing a runtime diagnostic of questionable usefulness.

Thoughts?

-Tom Wenisch
Computer Achitecture Lab
Carnegie Mellon University