Re: [Boost-users] fusion quesion

Subject: Re: [Boost-users] fusion quesion
From: Joel de Guzman (joel_at_[hidden])
Date: 2011-11-24 00:40:21

On 11/24/2011 1:07 PM, Robert Ramey wrote:
> Fusion includes a number of binary functions such as join, equal, less, etc.
> 
> Looking at the code suggests that they just work element by element in 
> sequential order.
> 
> But what about associative tuples?  For example
> 
> struct account {};
> struce amount {};
> 
> typedef  boost::fusion::set<
>     account,
>     amount
>> debit;
> 
> typedef boost::fusion::set<
>     amount,
>     account
>> debit2.
> 
> clearly the types are meant to be the "same" so I would expect
> 
> boost::fusion::join(debit, debit2) to function and return one type.
> I'm thinking it doesn't do that.  Any observations/suggestions that any 
> Fusion
> guru would like to share would be appreciated.

Join simply creates a joint_view which concatenates debit and debit2:

  joint_view<debit, debit2>

What you probably want are set operations such as set_union.
Unfortunately, we do not have those yet. Such set operations
should be cool to implement if anyone is interested in contributing.

Regards,
-- 
Joel de Guzman
http://www.boostpro.com
http://boost-spirit.com