AquaCurry - even though I have turned my back on Haskell and its relatives, I can't quite let go. Curry is another representative from the broad field of functional languages, although it is also represented in the area of logic-based languages (i.e., the area where Prolog and its relatives are often found). And there is a GUI environment for the Mac. In addition, the project is based at the University of Münster, and the part is called Münster Curry Compiler. Of course, I have to take a look at it.