Re: [boost] [mpl] Integral Constant is over specified

From: Andy Little (andy_at_[hidden])
Date: 2006-07-28 09:28:51

"David Abrahams" <dave_at_[hidden]> wrote in message
news:umzaulykv.fsf_at_boost-consulting.com...
> "Andy Little" <andy_at_[hidden]> writes:
>
>> A bool_ is stated to be a model of Integral Constant, but it patently doesnt
>> and
>> can never meet the next / prior requirements.
>
> Well, that's not strictly true.  false_ and true_ can meet the
> next/prior requirements just as well as int_<INT_MIN> and
> int_<INT_MAX> can.

Which is that they cant, so the statement is strictly true, INT_MIN and INT_MAX
arent models of Integral Constant either, similar for unsigned types.

> Any bounded type has the same problem; maybe we need to be more
> precise about what happens at the endpoints of the range.

I have found it essential  for  maths on a compile time rational, but its more
critical there.

As regards bool_ , the debate is interesting for theoreticians but for practical
programmers, it should be a separate Concept .. simple and many of the
type_traits functions should use that, which would remove the need for the
true_or_false_type mullarkey.

Also I suspect that the change from boost::is_same to std::is_same is going to
break a lot of code, unless the mpl tag requiremnet is lifted ;-)

regards
Andy Little