1. 1
2. 2
3. 3
4. 4
5. 5
6. 6
7. 7
8. 8
9. 9
10. 10
11. 11
12. 12

def mapM [Monad m] (f : α → m β) : List α → m (List β)
  | [] => pure []
  | x :: xs =>
    f x >>= fun hd =>
    mapM f xs >>= fun tl =>
    pure (hd :: tl)


#eval mapM (m := Id) (· + 1) [1, 2, 3, 4, 5]

#eval show IO Unit from IO.println "hello world"
#reduce show IO Unit from IO.println "hello world"