EX11: a GUI in a concurrent functional language

In this paper, I describe how GUIs can be made from collections of communicating parallel processes. The paper describes EX11 which is an Erlang binding to the X protocol. I describe the X windows programming model and show how X protocol messages can be naturally mapped onto Erlang messages. The code to perfom this mapping makes extensive use of the Erlang bit syntax and as such provides a good example of the use of the bit syntax to implement a reasonably complex protocol. I give code examples which make use of the EX11 widget library and show how the widget library itself is implemented.