Re: [Boost-users] variant over base and derived classes

Subject: Re: [Boost-users] variant over base and derived classes
From: Hicham Mouline (hicham_at_[hidden])
Date: 2010-12-09 10:22:39

>>-----Original Message----- 
>>From: "Diederick C. Niehorster" [dcnieho_at_[hidden]] 
>>Date: 09/12/2010 01:51 PM 
>>To: boost-users_at_[hidden] 
>>Subject: Re: [Boost-users] variant over base and derived classes 
>>(sorry if this is a top post, my phone shows no msg quotes) 
>>I'm no expert on this, but isn't there an compile time function to 
>>testing if an instance is derived from another (in introspection or 
>>something)? You could then maybe sort the variant types for most to 
>>least derived and then test untill you find the suitable cast? 
>>Just brainstorming pretty much. Hope its useful! 
>>Best, 
>>Dee 
>yes, there is boost::is_base_of or some metafct like that in type_traits. 
>not quite sure how to implement the sort though? 
>will checkout mpl::sort with binary predicate base_or_derived. 
>I have under 10 types, so compile time should be ok 
>thanks, 

This works. The source is pasted below.
I am however obliged to
1. declare a default-constructed variant
2. call mpl::for_each on the sequence of types in the variant a assign functor to assign to the variant.

Is there a way I can embed/simplify this 2 stage construction?

regards,