Composing the user interface with Haggis

This tutorial presents Haggis, a graphical user interface framework written in the lazy functional language Haskell. The Haggis framework provides the programmer with a compositional view of graphical user interfaces, where complete GUI applications can be built by repeatedly composing together parts. The individual user interface components are treated as virtual I/O devices that can be interacted with by the application just files and other `normal' devices. A key ingredient of Haggis is the use of concurrency to provide its compositional view of GUIs. 1 Introduction An important and interesting application area is graphical user interface applications. Haggis[6] is one Haskell[5] framework for composing such GUI applications within a functional language. Apart from being anchored in a lazy functional language, some of the important features of Haggis are: ffl A graphical user interface is treated as a virtual I/O device. A very common way of structuring a graphical user interface p..