Re: [boost] Ranged type mini-library submission

From: christopher diggins (cdiggins_at_[hidden])
Date: 2004-05-16 11:56:00

----- Original Message ----- 
From: "Christoph Ludwig" <cludwig_at_[hidden]>
To: <boost_at_[hidden]>
Sent: Sunday, May 16, 2004 12:21 PM
Subject: Re: [boost] Ranged type mini-library submission

> On Sun, May 16, 2004 at 11:07:22AM -0400, christopher diggins wrote:
> > From: "Jeff Garland" <jeff_at_[hidden]>
> > > On Sat, 15 May 2004 22:37:43 -0400, christopher diggins wrote
> > > > // you can explicitly turn off range_checking
> > > > #ifdef BOOST_RANGE_CHECKING_OFF
> > > > #define BOOST_RANGE_CHECKING_ON 0
> > > > #else
> > > > #define BOOST_RANGE_CHECKING_ON 1
> > > > #endif
> > >
> > > Again what happens if I want to change it for some, but not all my
> > constrained
> > > types.
> >
> > On this point, I am not convinced that it is important to make this
> > specifically a policy. I can only imagine the usage of this kind of
switch
> > for debug versus release code. Switching on a BOOST_RANGE_CHECKING
policy
> > for only some types strikes me as rather pathological.
>
> You may be right if all the range checking policy can do is
> signaling an error - I am not sure. But I can imagine applications
> where you'd like a saturating range checking policy, i.e. the input
> value is replaced by the maximum or minimum valid value. Or you need a
> periodic behaviour where the input value is projected onto an
> interval.
>
> OTOH, I may be falling into the trap of over-engineering.

You bring up a good point, but the conditional can also be introduced
directly into the error policy.

There are three options as I see it:
1) always apply check
2) have a macro as in the currrent version
3) have a separate policy for check

The arguments against number three (that I see) are:
- redundancy: conditional checking can be accomplished by the error policy.
- increases complexity
- introduces potential errors which would be very difficult to identify and
track down

It seems that the macro is not particularly attractive and could interfere
with certain specialized usages of constrained types, and would be
preferably dropped. Is this an accurate assesment?

Christopher Diggins
http://www.cdiggins.com
http://www.heron-language.com