Re: [boost] feature request for optional

From: David Abrahams (dave_at_[hidden])
Date: 2006-08-07 10:20:37

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.

HTH,
Dave

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com