```
exercises.hs:33:13:
    Couldn't match expected type ‘[b0]’ with actual type ‘a’
      ‘a’ is a rigid type variable bound by
          the type signature for myOrderFunc :: a -> a -> Ordering
          at exercises.hs:31:16
    Relevant bindings include
      y :: a (bound at exercises.hs:32:15)
      x :: a (bound at exercises.hs:32:13)
      myOrderFunc :: a -> a -> Ordering (bound at exercises.hs:32:1)
    In the first argument of ‘myLen’, namely ‘x’
    In the first argument of ‘(<)’, namely ‘myLen x’
Failed, modules loaded: none.
```

Your guess is correct. The problem is, Haskell does not consider `a` in `myOrderFunc` and `[b]` in `myLen` equivalent. `a` means you feed the function any type, while `[b]` means it must be a list of values of the same type. So changing `a` to `[a]` woud eliminate the error.