Functors are indeed a poor substitute for typeclasses if I want ad-hoc polymorphism. If I want ad-hoc polymorphism, I want typeclasses. I find Scala's implicits

Functors are indeed a poor substitute for typeclasses if I want ad-hoc polymorphism. If I want ad-hoc polymorphism, I want typeclasses. I find Scala's implicits to be a poor substitute (though not as poor as functors), and I'm sceptical that modular implicits are going to compare to typeclasses. But that's not why I care about functors. I use functors to package a bunch of types and values in a way that depends on a package of other types and values, which was their purpose from the beginning. In Haskell, I often want to do just this, but I find typeclasses (and associated types etc) to be a poor substitute for functors. For this reason, I keep an eye on backpack.