Re: [boost] feature request for optional

From: Sascha Krissler (boost-dev_at_[hidden])
Date: 2006-08-07 12:10:36

On Mon, Aug 07, 2006 at 10:20:37AM -0400, David Abrahams wrote:
> Sascha Krissler <boost-dev_at_[hidden]> writes:
> 
> >
> > Another solution would be to make a detail::generic_optional with all
> > the operator foo and let optional inherit from it.
> > That would be infinitesimal backward-incompatible ;)
> 
> I would use a simple metafunction to transform a type T into a type
> with a null value:
> 
>   template <class T>
>   struct nullable
>   {
>        typedef boost::optional<T> type;
>   };
> 
>   template <class T>
>   struct nullable<T*>
>   {
>        typedef T* type;
>   };
> 
>   // other specializations for types with built-in NULL values
> 
> This way you're really not incurring any overhead for types that are
> already nullable.  Use free functions to smooth out any messy
> interface differences due to the optional<T> wrapper on some types.
> 
That's what i am doing right now.
The messy interface differences could be smoothed out by optional<>.
If i had to implement all the interface of OptionalPointee again
that would be a lot of duplication whether changing optional would
be a couple of mpl::if_.
Well i will not wait for a new release of boost to solve my poblem anyway
it is a suggestion to improve the genericity of the lib.