Re: [boost] Re: boost/mpl/integral_c.hpp and Borland

From: David Abrahams (dave_at_[hidden])
Date: 2003-02-03 16:40:45

"Fernando Cacciola" <fernando_cacciola_at_[hidden]> writes:

> ----- Original Message -----
> From: "David Abrahams" <dave_at_[hidden]>
> To: "Beman Dawes" <bdawes_at_[hidden]>
> Cc: "boost" <boost_at_[hidden]>; "Aleksey Gurtovoy"
> <agurtovoy_at_[hidden]>; "Fernando Cacciola" <fcacciola_at_[hidden]>
> Sent: Friday, January 31, 2003 9:58 PM
> Subject: [boost] Re: boost/mpl/integral_c.hpp and Borland
>
>
>> Beman Dawes <bdawes_at_[hidden]> writes:
>>
>> > Dave,
>> >
>> > Your change to boost/mpl/integral_c.hpp broke a lot of
>> > Borland 5.61 compiles.
>>
>> I thought something like that might happen on the broken compilers.  I
>> don't really know what the best approach here might be, other than to
>> take out casts for those compilers.  I'm not even sure if
>> integral_c<some_enum,...> (which is what the change accomodates) is
>> appropriate.  Perhaps we should have enum_c with no next,prior for
>> this purpose.
>>
> I see that integral_c<> has been fixed now.
> I'm puzzled though about why the apparently simple fix didn't worked on
> Borland.
> On bcc5.5.1, it says: Cannot cast from 'T' to 'T' (!?)

What happens if you replace it with a C-style cast?

> Anyway, I'd like to know what is the role of integral_c<>; in particular,
> with respect to 'int_c<>'.

int_c<> is a convenience that prevents you from having to write
integral_c<int, ...>

> IOWs, why does it has next/prior?

That one's for Aleksey.

> I know that you could pass an integral_c<> to a metafunction which would
> operate on a generic Integral metavalue, doing ::next for instance; but my
> question is: when and why would you pass 'integral_c<>' instead of
> 'int_c<>'?

If you want unsigned long, signed char, unsigned short, etc... values.
-- 
                       David Abrahams
   dave_at_[hidden] * http://www.boost-consulting.com
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