Odersky wrote a simple implementation, and it looks a lot nicer. It also doesn't use any casts or implicit conversaions: https://gist.github.com/odersky/6b7c0eb4731058803dfd

True. In retrospect, trying to make the Scala transducer type look like Haskell and then hacking into working order was didn't do justice to either language. As I sort of note in the text, the attempt to do it this way was at least partially meant to be "amusing."