Re: [Boost-users] MPL intersection of type sequences and compile-time performance

From: David Abrahams (dave_at_[hidden])
Date: 2007-06-11 00:18:56

on Sun Jun 10 2007, Andrej van der Zee <mavdzee-AT-yahoo.co.uk> wrote:

> Hi,
>
> Than you for the quick reply :) Now I reimplemented
> intersect by converting the type sequences to mpl::set
> and do a mpl::has_key instead of mpl::contains:
>
> template <typename seq1, typename seq2>
> struct intersect
> {
>   typedef typename copy<seq2
>      , inserter< set<>, insert< _1, _2 > >
>      >::type set_seq2;
>
>   typedef typename copy_if<seq1
>      , has_key <set_seq2, _1> 
>      , back_inserter < vector<> >
>      >::type type;
> };
>
> Now I would like to optimize this and only convert to
> a set if the type sequence does not support
> mpl::has_key. How should I do this?

I don't know, frankly.  

> I looked at the mpl::sequence_tag<seq2> but I am not
> sure how to use this. Nor if this is the right way to
> do this. Could you please help?

Maybe Aleksey can help.  Sorry I couldn't.

-- 
Dave Abrahams
Boost Consulting
http://www.boost-consulting.com