TL;DR As noted earlier, transducers can be properly annotated in Clojure using core.typed and they probably should be. But... there are a few tricks necessary to make it work. Transducers in Scala require tricks too, but different ones. Oh, but they're so lovely in Haskell. Update 2015-01-12 Were you led here by Clojure Gazette? Eric Normand is usually more discriminating, but don't worry, this wi