Abstract. Although computer systems penetrate all facets of society, the software running those systems may contain many errors. Producing high quality software appears to be difficult and very expensive. Even determining the quality of software is not easy. Testing is by far the most used way to estimate the quality of software. Testing itself is not easy and time consuming. In order to reduce the costs and increase the quality and speed of testing, testing should be automated itself. An automatical specification based test tool generates test data, executes the associated tests, and makes a fully automatically verdict based on a formal specification. Advantages of this approach are that one specifies properties instead of instances of these properties, test data are derived automatically instead of manually, the tests performed are always up to date with the current specification, and automatic testing is fast and accurate. We will show that functions in a functional programming language can be used very well to model properties. One branch of the automatic test system Gast handles logical properties relating function arguments and results of a single function call. The other branch of Gast handles specifications of systems with an internal state. 1

Abstract. We present a uniqueness type system that is simpler than both Clean’s uniqueness system and a system we proposed previously. The new type system is straightforward to implement and add to existing compilers, and can easily be extended with advanced features such as higher rank types and impredicativity. We describe our implementation in Morrow, an experimental functional language with both these features. Finally, we prove soundness of the core type system with respect to the call-by-need lambda calculus. 1 Introduction to Uniqueness Typing An important property of pure functional programming languages is referential transparency: the same expression used twice must have the same value twice. This makes equational reasoning possible and aids program analysis, but most languages do not have this property. For example, in the following C fragment,

Abstract. We present an application of functional programming in the domain of sound generation and processing. We use the lazy language Clean to define purely functional stream generators, filters and other processors, such as reverberators. Audio signals are represented (before the final output to arrays processed by the system primitives) as co-recursive lazy streams, and the processing algorithms have a strong dataflow taste. This formalism seems particularly appropriate to implement the ‘waveguide’, or ‘physically-oriented ’ sound models. Lazy programming allocates the dynamical memory quite heavily, so we do not propose a real-time, industrial strength package, but rather a pedagogical library, offering natural, easy to understand coding tools. We believe that, thanks to their simplicity and clearness, such functional tools can be also taught to students interested in audio processing, but with a limited competence in programming.

Abstract. Although computer systems penetrate all facets of society, the software running those systems may contain many errors. Producing high quality software appears to be difficult and very expensive. Even determining the quality of software is not easy. Testing is by far the most used way to estimate the quality of software. Testing itself is not easy and time consuming. In order to reduce the costs and increase the quality and speed of testing, testing should be automated itself. An automatical specification based test tool generates test data, executes the associated tests, and makes a fully automatically verdict based on a formal specification. Advantages of this approach are that one specifies properties instead of instances of these properties, test data are derived automatically instead of manually, the tests performed are always up to date with the current specification, and automatic testing is fast and accurate. We will show that functions in a functional programming language can be used very well to model properties. One branch of the automatic test system Gast handles logical properties relating function arguments and results of a single function call. The other branch of Gast handles specifications of systems with an internal state. 1

Abstract—It can be argued that some of the benefits of purely functional languages are counteracted by the lack of efficient and natural-to-use data structures for these languages. Imperative programming is based on manipulating data structures destructively, e.g., updating arrays in-place; however, doing so in a purely functional language violates the language’s very nature. In this paper, we present a type and effect system for an eager purely functional language that tracks array usage, i.e., read and write operations, and enables the efficient implementation of purely functional arrays with destructive update. I.