How functional programming mattered

In 1989 when functional programming was still considered a niche topic, Hughes wrote a visionary paper arguing convincingly ‘why functional programming matters’. More than two decades have passed. Has functional programming really mattered? Our answer is a resounding ‘Yes!’. Functional programming is now at the forefront of a new generation of programming technologies, and enjoying increasing popularity and influence. In this paper, we review the impact of functional programming, focusing on how it has changed the way we may construct programs, the way we may verify programs, and fundamentally the way we may think about programs

A Functional Approach to Hardware Software Co-Design

Developing software for embedded systems presents quite the challenge---not only do these systems demand good knowledge of the hardware they run on, but their limited resources also make it difficult to achieve efficiency. For embedded systems with different kinds of processing elements, the challenge is even greater; the presence of heterogeneous elements both raises all of the issues associated with homogeneous systems, and may also cause non-uniform system development and capability.In this thesis we explore a functional approach to heterogeneous system development, with a staged hardware software co-design language embedded in Haskell, to address many of the modularity problems typically found in such systems. This staged approach enables designers to build their applications from reusable components and skeletons, while retaining control over much of the generated source code. Design exploration also benefits from the functional approach, since Haskell\u27s type classes can be used to ensure that certain operations will be available. As a result, a developer can not only write for hardware and software in the co-design language, but she can also write generic programs that are suitable for both.Internally, the co-design language is based on a monadic representation of imperative programs that abstracts away from its underlying statement, expression, and predicate types by establishing an interface to their respective interpreters. Programs are thus loosely coupled to their underlying types, giving a clear separation of concerns. The compilation process is expressed as a series of translations between progressively smaller typed languages, which safeguards against many common errors.In addition to the hardware software co-design language, this thesis also introduces a language for expressing digital signal processing algorithms, using a model of synchronous data-flow that is embedded in Haskell. The language supports definitions in a functional style, reducing the gap between an algorithm\u27s mathematical specification and its implementation. A vector language is also presented, which builds on a functional representation that guarantees fusion for arrays. Both of these languages are intended to be extensions of the co-design language, but neither one is dependent on it and can thus be used to extend other languages as well

A generic abstract syntax model for embedded languages

Representing a syntax tree using a data type often involves having many similar-looking constructors. Functions operating on such types often end up having many similar-looking cases. Different languages often make use of similar-looking constructions. We propose a generic model of abstract syntax trees capable of representing a wide range of typed languages. Syntactic constructs can be composed in a modular fashion enabling reuse of abstract syntax and syntactic processing within and across languages. Building on previous methods of encoding extensible data types in Haskell, our model is a pragmatic solution to Wadler\u27s "expression problem". Its practicality has been confirmed by its use in the implementation of the embedded language Feldspar