. We describe a process extension to a lazy functional programming system, intended for applications with graphical user interfaces (GUIs). In the extended language, dynamically-created processes communicate by asynchronous message passing. We illustrate the use of the language, including as an extended example a simple board game in which squares are implemented as concurrent processes. We also describe a window manager, itself implemented in the extended functional language. Keywords: functional language, processes, concurrency, window manager, Gofer. 1 Introduction and Motivation Most of the time, elements of a graphical user interface (GUI) operate independently. For example, a menu doesn't interact with the rest of the program until the user selects an option. The user can highlight options, open up further menus or move the menu around the screen, all without doing anything that should concern any other element of the program. Popular languages such as C do not readily lend the...

In this paper we describe the implementation of several graphical programming paradigms (Model View Controller, Fudgets, and Functional Animations) using the GUI library TkGofer. This library relies on a combination of monads and multiple-parameter type classes to provide an abstract, type safe interface to Tcl/Tk. We show how choosing the right abstractions makes the given implementations surprisingly concise and easy to understand.

. 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...

The Glasgow Haskell compiler provides a foreign language interface which allows Haskell programs to call arbitrary C functions. This has been used both to implement the standard Haskell IO system and a variety of applications including an arcade game [8], and a graphical user interface to a database [19]. The theoretical problems associated with using impure functions from pure functional languages are avoided through the use of monads [17]; and the mismatch between strict languages with no garbage collection and lazy languages with garbage collection is tackled by unboxing (that is, forcing evaluation of arguments and stripping off any header information) [15]. Whilst this works well for simple examples, it is unsuitable when one wants to pass arguments (or results) which are lazy, polymorphic or very large. We describe two extensions to the garbage collector which solve these problems by allowing better interaction between the Haskell garbage collector and memory allocation in the im...

There are a number of systems that advocate the use of lazy functional languages for the programming of graphical user interfaces (GUIs) such as Haggis, Gadgets, and Fudgets. These systems have addressed similar issues, such as how to handle I/O in a purely functional language, and how to provide a structured interface to the event driven model of windowing systems. In this report we present a framework that encapsulates such common elements and is intended to aid in the formal study of the relationships between these systems. The framework is called Embracing Windows, partly because it embraces the window paradigm, and partly because it uses the Hugs functional programming system. Two high-level GUI development systems have been built on the framework, and are based upon Haggis and Fudgets, respectively. The essence of these systems is distilled and a brief comparison made. The complete Haskell source code for the Embracing Windows framework is presented as an appendix. The framework ...

Mere academic toys or the tools of the future? Lazy functional programming languages have undoubted attractive properties. This thesis explores their potential, from the programmer's point of view, for implementing interactive and graphical applications to which they do not seem immediately suited. The discussion is centred round two example applications. One is a graphical design program based on an idea of the artist M. C. Escher. The thesis argues that the graphical user interface may be encapsulated in an "interpret " function that when applied by a mouse click to an interface of appropriate type yields the required behaviour. The second example is a monitoring interpreter for a functional language. The idea is that if the mechanics of the reduction are presented at a suitable level of abstraction, this may be used to give insight into what is going on. On the basis of this the programmer might modify the code so that a program runs more efficiently in terms of speed and memory requirements. Problems of displaying the reduction are addressed, and solutions proposed for overcoming these: displaying the graph as a spanning tree, to ensure planarity, with extra leaves

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