Re: [boost] Formal review or Variant Library (Ed B.)

From: David Abrahams (dave_at_[hidden])
Date: 2003-02-19 10:33:37

"Peter Dimov" <pdimov_at_[hidden]> writes:

> David Abrahams wrote:
>> "Peter Dimov" <pdimov_at_[hidden]> writes:
>> 
>>> It may be possible to use optional<T&> (is it supported?) or
>>> optional< reference_wrapper<T> > but this looks like an "obfuscated
>>> C++" entry to me compared to T*.
>> 
>> Good point.
>> 
>>> What's wrong with it? What does optional<T&> add?
>> 
>> Suppose you have a
>> 
>>      variant<mpl::list<int&, std::string&> >
>> 
>> How do you check to see if it contains an int&?
>
> You don't. "int&" doesn't meet the variant requirements. 

Too bad.  Could be very useful, just like a tuple of references is
useful.

> Even if it did:
> 
> variant< int, int& > v;
>
> How do you check to see if it contains an int&?

I don't know, maybe:

      optional<exactly<int&> > w = v;

??

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