learning-haskell/16-functor/16.17-chapter-exercises.md

Chapter Excercises

Can a valid Functor be written?

1. No, Bool is of kind *
2. Yes, see src/chptexc.hs
3. Yes, see src/chptexc.hs
4. The first f in outF :: f (Mu f) implies that f is of kind * -> *. Mu takes this f to return a type, so it's kind is (* -> *) -> *. This means we can't make a Functor from this as this is not * -> *
5. No, D is of kind *

Rearrange

see src/chptexc.hs

Write

see src/chptexc.hs