Abstract not found

Abstract not found

The interface with the outside world has always been one of the weakest points of functional languages. It is not easy to incorporate I/O without being allowed to do side-effects. Furthermore, functional languages allow redexes to be evaluated in any order while I/O generally has to be performed in a very specific order. In this paper we present a new solution for the I/O problem which we have incorporated in the language Concurrent Clean. Concurrent Clean offers a linear type system called Unique Types . It makes it possible to define functions with side-effects without violating the functional semantics. Now it is possible to change any object in the world in the way we wanted: e.g. arrays can be updated in-situ, arbitrary file manipulation is possible. We have used this powerful tool among others to create a library for window based I/O. Using an explicit environment passing scheme provides a high-level and elegant functional specification method for I/O, called Event...

Abstract. This paper presents a transformational approach to the derivation of implementations from model-oriented specifications of abstract data types. The purpose of this research is to reduce the number of formal proofs required in model refinement, which hinder software development. It is shown to be applicable to the transformation of models written in Meta-iv (the specification language of Vdm) towards their refinement into, for example, Pascal or relational DBMSs. The approach includes the automatic synthesis of retrieve functions between models, and data-type invariants. The underlying algebraic semantics is the so-called final semantics “à la Wand”: a specification “is ” a model (heterogeneous algebra) which is the final object (up to isomorphism) in the category of all its implementations. The transformational calculus approached in this paper follows from exploring the properties of finite, recursively defined sets. This work extends the well-known strategy of program transformation to model transformation, adding to previous work on a transformational style for operationdecomposition in META-IV. The model-calculus is also useful for improving model-oriented specifications.

A Functional Database Phil Trinder D.Phil. Thesis Wolfson College Michaelmas Term, 1989 This thesis explores the use of functional languages to implement, manipulate and query databases. Implementing databases. A functional language is used to construct a database manager that allows efficient and concurrent access to shared data. In contrast to the locking mechanism found in conventional databases, the functional database uses data dependency to provide exclusion. Results obtained from a prototype database demonstrate that data dependency permits an unusual degree of concurrency between operations on the data. The prototype database is used to exhibit some problems that seriously restrict concurrency and also to demonstrate the resolution of these problems using a new primitive. The design of a more realistic database is outlined. Some restrictions on the data structures that can be used in a functional database are also uncovered. Manipulating databases. Functions over the database a...

Data-parallel programming languages have many desirable features, such as single-thread semantics and the ability to express fine-grained parallelism. However, it is challenging to implement such languages efficiently on conventional MIMD multiprocessors, because these machines incur a high overhead for small grain sizes. This paper presents compile-time analysis techniques for data-parallel program graphs that reduce these overheads in two ways: by stepping up the grain size, and by relaxing the synchronous nature of the computation without altering the program semantics. The algorithms partition the program graph into clusters of nodes such that all nodes in a cluster have the same loop structure, and further refine these clusters into epochs based on generation and consumption patterns of data vectors. This converts the fine-grain parallelism in the original program to medium-grain loop parallelism, which is better suited to MIMD machines. A compiler has been implemented based on th...

Existing techniques for garbage collection and machine code optimizations can interfere with each other. The inability to fully optimize code in a garbage-collected system is a hidden cost of garbage collection. One solution to this problem is proposed; an inexpensive protocol that permits most optimizations and garbage collection to coexist. A second approach to this problem and a separate problem in its own right is to reduce the need for garbage collection. This requires analysis of storage lifetime. Inferring storage lifetime is di#cult in a language with nested and recursive data structures, but it is precisely these languages in which garbage collection is most useful. An improved analysis for "storage containment" is described. Containment information can be represented in a directed graph. The derivation of this graph falls into a monotone data-flow analysis framework; in addition, the derivation has the Church-Rosser property. The graphs produced in the analysis of a value-a...

. We review the basics of functional programming, and give a brief introduction to emerging techniques and approaches relevant to building real-time software. In doing so we attempt to explain the relevance of functional programming concepts to the real-time applications domain. In particular, we address the use of types to classify properties of real-time computations. "If thought corrupts language, language can also corrupt thought." George Orwell, Politics and the English Language 1

Abstract. The subject of this paper is functional program transformation in the so-called point-free style. By this we mean first translating programs to a form consisting only of categorically-inspired combinators, algebraic data types defined as fixed points of functors, and implicit recursion through the use of type-parameterized recursion patterns. This form is appropriate for reasoning about programs equationally, but difficult to actually use in practice for programming. In this paper we present a collection of libraries and tools developed at Minho with the aim of supporting the automatic conversion of programs to point-free (embedded in Haskell), their manipulation and rule-driven simplification, and the (limited) automatic application of fusion for program transformation. 1

The purpose of the Adl project is to demonstrate the efficient implementation of data parallel functional programming, firstly on the TMC CM-5 but ultimately on other parallel machines. We have designed a small polymorphic non-recursive language (Adl), which emphasizes high-level operations (second-order combinators) on aggregate structures. The Adl project incorporates the formal description of Adl semantics, translation and optimization, and the design of an abstract data-parallel machine which describes not only the CM-5 but also other distributed memory multicomputers and hence encourages architecture-independent code generation. An executable natural semantic description of translation to the Bird-Meertens Formalism (BMF) has been completed; similar techniques are being used with an optimizer. We also describe an implementation of the abstract machine for the CM-5 implementation. 1 Introduction Exploitation of parallelism in applications is a very attractive concept, but there is...