[boost] Re: [variant, MPL] Is there a variant -> mpl sequence metafunction ?

From: Larry Evans (cppljevans_at_[hidden])
Date: 2005-05-17 22:22:54

On 05/17/2005 10:07 PM, Jaakko Järvi wrote:
> make_variant_over<Seq>::type
> 
> creates a variant type from an MPL Sequence.
> 
> Is there an operation that would do the opposite, create an MPL sequence 
> from a variant?
> 
> I cannot just use the type parameter list as such because the types that 
> stand for an empty
> type are different in both libraries: boost::detail::variant::void_ in 
> variant, and something
> else in MPL.
I'd suggest making variant part of mpl.  With that, the problem
disappears.  Also, variant and tuple are duals of each other, in
category theory terms; hence, it would make sense if the implementations
reflected this duality.  The code at:

http://cvs.sourceforge.net/viewcvs.py/boost-sandbox/boost-sandbox/boost/indexed_set/?hideattic=0

is an intial attempt at exploiting this duality.