I'm not sure about haskell, but in clojure the, run code, reason, run more code cycle is very much supported with the repl.

In fact I find the nature of functional code very much helps out here. With clojure, in a complicated system I can typically take any subcomponent and run it in the repl without much fuss/mocking or worrying about the state of the system. Since usually functions aren't modifying state I can rerun, modify, rerun over and over again without restarts.