on 2/20/01 3:36 PM, Howard Hinnant at hinnant@[...].. wrote:

>  Daryle Walker wrote on 2/20/01 2:48 PM
> > The char type is supposed to be like either signed char or unsigned
> > char, which one is implementation defined. Similarly, the wchar_t type
> > is supposed to be like one of the other integral types, which one is
> > implementation defined. Could we have some sort of structure indicating
> > those types' base types? I guess it would be something like:
[SNIP example]

> > How would we figure out the types? I guess something using <climits> macros
> > and/or comparisons from <limits> values would be used. What header would
> > this go under, type_traits.hpp or a new one?
> 
>  I'm sure this could be done with <climits> macros. But the following
>  might be more fun! :-)
[SNIP big example with a bunch of old and hopeful class templates]

I don't necessarily need something big & fun, maybe something quick & dirty
will do -_^. This is what I have so far:

//=========================================================================
template <class T, class B = ::boost::detail::empty_base> 
struct character_convertible : B
{
operator char() const
{
#if CHAR_MIN == 0
return static_cast<unsigned char> ( static_cast<const T&>(*this) );
#else
return static_cast<signed char> ( static_cast<const T&>(*this) );
#endif
}

#ifndef BOOST_NO_INTRINSIC_WCHAR_T
operator wchar_t() const
{
// The underlying type here is a complete guess. Help!
return static_cast<unsigned short> ( static_cast<const T&>(*this) );
}
#endif
};
//=========================================================================

(It's from an upcoming version of the operators.hpp header.)

BTW, where does the BOOST_LONGLONG_SUPPORT come from? I didn't see it in
the latest config.hpp on CVS. Is this also a wish? For now, I #include
<climits>  and check if ULLONG_MAX and/or LLONG_MAX exist.

>  Seems like I've seen someone talk about a integral best fit lib that
>  might simplify all the if'ing I'm doing in the wchar_t specialization,
>  but alas I can't remember who or where.

Could you be talking about the /boost/integer.hpp header, which lets an
user pick the best integral type for a certain bit size? I started that
discussion for the CRC stuff. I've thought of it, but I would have to
somehow incorporate the signed/unsigned determination.

>  After all that, this is not a comment on your first question of whether
>  such a struct should be part of boost. It is simply a sample
>  implementation.

If it's just for my quick needs above, it could just stay in that header. I
guess that someday someone else might need that information.

--
Daryle Walker
Mac, Internet, and Video Game Junkie
darylew AT mac DOT com