Deduplicating types in a list

[spayne-pgh]

We're looking at using Metal to replace an in-house type list implementation and one of the features that we use is to deduplicate types in a list. Looking at boost::mp11, there's a dedicated mp_unique template that will do that out-of-the box. But, we'd like to avoid boost if we could, just because of the size. Is there a ready-made solution for deduplicating types in a metal::list or would we have to roll our own?

[brunocodutra]

Hey @spayne-pgh, glad to hear you're considering Metal. An implementation of unique is not currently available out of the box, but can be easily implemented out of the primitives Metal offers, in fact it's a short one-liner:

template<class seq>
using unique = accumulate<bind<lambda<if_>, lambda<contains>, _1, lambda<append>>, list<>, seq>;

You can try it live on compiler explorer, is that what you were looking for?

[spayne-pgh]

Nice, that's an excellent one-liner. Thanks for the quick reply.