Haskell type-level projection -

is there way of defining type level projection without using type families?

i so:

{-# language typefamilies #-} type family project t :: * type instance project [r] = r , 

but ever use 1 instance of it.

you can use multiparamtypeclass , functionaldependencies, though without knowing why you're using it's hard if sufficient.

class project k | k -> instance project [r] r  > :t undefined :: project string r => r undefined :: project string r => r :: char