@ctongfei I think this is a very sensible suggestion. These type classes are pretty much settled and AFAICT an obvious improvement on the ones in the current stdlib.
I also think e.g. Semigroup/Monoid are pretty much settled in terms of basic algebra, but I wonder: is the resistance to inclusion in stdlib a matter of the “encoding” of these things?
EDIT: Generally speaking (as an FP-all-the-way person!), I think FP-in-Scala is missing out in a huge way by not having ‘standard’ Functor, Applicative, Monad type classes, etc. I do understand the maintainer reluctance since it seems that Scala 3 might make things a lot less contentious wrt. ‘encoding’, etc.