WxHaskell

wxHaskell is a portable and native graphical user interface (GUI) library for the programming language Haskell, built on wxWidgets. It is often used by those wanting to develop a GUI with a functional programming language.

High-level GUI libraries built on wxHaskell
wxHaskell is a middle-level GUI library. Several experimental high-level GUI library approaches are implemented on wxHaskell: In contrast, the high-level GUI libraries FG and Grapefruit are implemented on the middle-level Gtk2Hs, which is based on GTK2.
 * Reactive-banana
 * FunctionalForms
 * wxFruit
 * Phooey

All of these high-level libraries are experimental, using advanced mathematics concepts in their approach (see arrows in functional programming).