[boost] Re: Problem with <boost/integer.hpp>, and request for extension

From: Daryle Walker (dwalker07_at_[hidden])
Date: 2002-11-11 22:08:29

On Monday, November 11, 2002, at 8:59 AM, Kevin S. Van Horn wrote:

> I have found that
>
>   boost::uint_t<64>::fast
>
> gives a compiler error even on a platform (RH 7.3 on Intel) that has
> 64-bit integers available (as long long).  On checking the 
> documentation
> again, it does specify this behavior, but this strikes me as quite
> unreasonable; if a platform has long long, I should be able to use it.

The reason it hasn't been added is that there is no guarantee that long 
long constants can be used at compile-time (since it's not officially 
part of C++).

> I believe that all that is needed to fix this is inclusion of the
> following lines:
>
> #ifdef BOOST_HAS_LONG_LONG
>   template <> struct int_least_helper<0>
>   { typedef long long least; };
> #endif
>
> #ifdef BOOST_HAS_LONG_LONG
>   template <> struct int_least_helper<5>
>   { typedef unsigned long long least; };
> #endif

The cases for 0 and 5 are left out deliberately so desired bit counts 
beyond any integer type give an error.  So a "fix" for this would have 
to _add_ two new cases, still leave two error cases, and work when a 
compiler doesn't have long long.

> Also, I'd like to see the following added to <boost/integer.hpp>:
>
> boost::signed_int<T>::type  -- Gives the signed integer type of the 
> same
>                                size as integer type T.
> boost::unsigned_int<T>::type -- Gives the unsigned integer type of the
>                                same size as integer type T.
>
> Rationale: I often find myself using
>   std::iterator_traits<Iterator>::difference_type
> for quantities that are guaranteed to be nonnegative; for these I would
> prefer to use an unsigned type.

Got a sample implementation?  I could think of

template < typename T >
struct unsigned_int
{
     typedef uint_t<sizeof(T) * CHAR_BIT>  type;
};