Lightweight GUIs for functional programming

Graphical user interfaces (GUIs) are hard to combine with functional programming. Using a suitable combination of monads, we are able to tame the imperative aspects of graphical I/O in a straightforward and elegant way. We present a concept to integrate lightweight GUIs into the functional framework, together with a library of basic functions and layout combinators to manipulate the GUI. An implementation of this library, using a set of high-level graphical I/O routines, is outlined. Examples demonstrate the simple way in which applications can be written.