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

on Sun Jun 10 2007, Andrej van der Zee wrote:

Hi,

Sorry if this already has been posted, but I have a problem with compile-time performance when trying to get the intersection of two type sequences. For example, when I do something like this:

template struct intersect { typedef typename boost::mpl::remove_if

...

::type type; };

typedef mpl::vector l1; typedef mpl::vector l2;

typename intersect::type my_intersection;

Then for large type sequences compile-time becomes unacceptable (O(M*N)).

I'm surprised it's even that good, since most compilers have such poor performance for multiple instantiations of the same template. That's the cost you'd expect for a direct runtime translation of your algorithm.

Is there a better way to do this?

I'd use an associative sequence like mpl::set. -- Dave Abrahams Boost Consulting http://www.boost-consulting.com