. The functional programming language Clean has a high level I/O system (version 0.8) in which complex yet efficient interactive programs can be created. In this paper we present its successor (version 1.0), the object I/O system. We consider some of the design considerations that have influenced the design of the new I/O system greatly. Key issues are compositionality, orthogonality, and extensibility. Apart from design, the object I/O system improves on its predecessor by two major contributions: programmers can introduce polymorphic local state at every (collection of) user interface component(s) and programmers can create interactive processes in a flexible way. All interface components can communicate with each other by sharing state but also using powerful message passing primitives in both synchronous, asynchronous, and uni- or bi-directional way. Using the message passing mechanism remote procedure calling can be added easily. The result is an object oriented I/O...

. Pure, functional programming languages oer several solutions to construct Graphical User Interfaces (GUIs). In this paper we report on a project in which we port the Clean Object I/O library to Haskell. The Clean Object I/O library uses an explicit environment passing scheme, based on the uniqueness type system of Clean. It supports many standard GUI features such as windows, dialogues, controls, and menus. Applications can have timing behaviour. In addition, there is support for interactive processes and message passing. The standard functional programming language Haskell uses a monadic framework for I/O. We discuss how the Object I/O library can be put in a monadic framework without loosing its essential features. We give an implementation of an essential fragment of the Object I/O library to demonstrate the feasibility. We take especial consideration for the relevant design choices. One particular design choice, how to handle state, results in two versions. 1 Intro...