[Haskell-cafe] Is there Functor instance of Enumerator'

Say i want to compose Enumerator ByteString m b and Iteratee Builder m b, so I try to transform the enum to Enumerator Builder m b, providing function ByteString -> Builder. It's like implement a Functor instance for Enumerator. But i failed, there are no way to make type system happy. Am I right that there is no Functor instance of Enumerator? -- http://www.yi-programmer.com/blog/