combine Type values

[gelisam]

It is possible to have a value of type Type containing the type constructor Maybe, and another value of type Type containing the type Integer. We should define an operation which combines them into a value of type Type containing the type (Maybe Integer).

Since this can fail (e.g. (Integer Maybe) should be rejected), this must be a macro action.

(>>= (apply-type (the-type Maybe) (the-type Integer))
  (lambda (maybe-integer)
    (case maybe-integer
      [(Maybe Integer) 'success])))

[gelisam]

@david-christiansen if failure is the only reason for apply-type to have type (-> Type Type (Macro Type)), would it perhaps make more sense for it to have type (-> Type Type (Maybe Type)) instead, like funResultTy in Haskell?