Re: [Boost-users] [Any] Operator ==

Subject: Re: [Boost-users] [Any] Operator ==
From: OvermindDL1 (overminddl1_at_[hidden])
Date: 2010-11-01 20:35:23

On Mon, Nov 1, 2010 at 9:16 AM, Nevin Liber <nevin_at_[hidden]> wrote:
> On 1 November 2010 08:57, Hossein Haeri <powerprogman_at_[hidden]> wrote:
>
>> Is there any way to implement an operator == (and perhaps also operator !=) for objects of type boost::any so that different instances are always != and an instance is always only == to itself -- regardless of the respective values?
>
>> In case you're wondering why I'd interested in such operators, the answer is that I'm thinking of storing objects of type boost::any in an unordered_map.
>
> Wouldn't this just be the address of the object (which isn't
> particularly useable as a key in a map)?

Actually it would be possible.  For example, Adobe's Any version has a
streaming operator (which throws I think if the stored type does not
support streaming, or just does not accept it, one or the other).  The
way it does it can easily be extended to handle a == of the internal
value (not just the type) as well.

Hmm, perhaps it is time for an extended Boost.Any that supports
'concepts' of a sort of the stored types.  Hmm, Boost.Proto could
probably simplify the scaffolding a lot as well...