Re: [Boost-users] [MPL] Filtering a sequence to leave only most-derived types

Subject: Re: [Boost-users] [MPL] Filtering a sequence to leave only most-derived types
From: Sebastian Redl (sebastian.redl_at_[hidden])
Date: 2010-02-25 07:39:02

Rutger ter Borg <rutger <at> terborg.net> writes:

> 
> Not sure, but I would do something like
> 
> typedef mpl::vector< A, B, C > m_vec;
> 
> typedef mpl::sort<
>     m_vec, 
>     boost::is_base_of< mpl::_1, mpl::_2 >
> >::type sorted_type;
> 
> typedef mpl::unique<
>     sorted_type,
>     boost::is_base_of< mpl::_1, mpl::_2 >
> >::type unique_type;

Thank you, I got to the solution with this. I considered using sort+unique at
first, but dismissed it because the predicate does not define a total order, and
because is_base_of is not a proper equivalence.. But apparently it works anyway.
I just had to reverse the condition (i.e. define a is_derived_from metafunction).

Sebastian