Re: [Boost-users] variant comparison operators

From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2008-03-28 12:52:23

AMDG

Jiri Palecek wrote:
> Hello,
>
> is there some deep reason why comparing variant to a nonvariant is  
> disabled? For example:
>
> variant<int, string> v=1;
> assert(v==1); // doesn't compile
>
> The problem is that there are overloads for anything else than a variant,  
> which explicitely fail to compile (via static_assert and other means). If  
> they weren't there, everything would work (the comparison would invoke  
> conversion constructor, and then normal variant/variant comparison.
>   

It seems to be an explicit decision.
http://svn.boost.org/trac/boost/changeset/19960
It is probably just to be the same as operator<
(See http://lists.boost.org/Archives/boost/2003/09/52425.php for a 
rationale)

> Another problem is that variant includes the == operator, but not !=, even  
> though this could be easily achieved with boost::operators.
>   
You're not the first to want this
http://lists.boost.org/Archives/boost/2006/06/105801.php

In Christ,
Steven Watanabe