The Gofer system is a functional programming environment for a small, Haskell-like language. Supporting a wide range of different machines, including home computers, the system is widely used, both for teaching and research. This report describes the main ideas and techniques used in the implementation of Gofer. This information will be particularly useful for work using Gofer as a platform to explore the use of new language features or primitives. It should also be of interest to those curious to see how the general techniques of functional programming language compilation are adapted to a simple, but practical, implementation.

. 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. 1 Introduction Everybody wants to use graphical user interfaces. And everybody wants to use functional programming languages. Unfortunately, these concepts are hard to combine: I/O, and graphical I/O in particular, is imperative in nature, and thus contradictory to the functional paradigm. Our goal is to reconcile these two concepts, by developing a framework in which a functional programmer smoothly can provide his program with a...