On 4/5/26 16:54, Emanuel Spiridon wrote:

> Yes, the proposal from 2018 is quite similar to mine, however that
> proposal is trying to standardize Boost.Mp11 as a general purpose meta
> programming toolkit.
> P0949 was proposed in 2018 but was not adopted, and predates C++20
> concepts entirely.

My point was that having a type algorithm (contains) that only works
with a dedicated type-list type rather than arbitrary templates means
that the type algorithm has limited utility.

> I am proposing the minimal building blocks needed for named, composable
> type sets for concept constraints, without requiring users to learn a
> full meta programming library.

Another proposal that looks a lot like yours is

   https://wg21.link/N4115

It may be worth investigating why this was not adopted.

About your proposal, the subsumption example using numbers is not great,
because we already have std::is_arithmetic for that.