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Towards modular compilers for effects pdfbibtex Laurence E. Day and Graham Hutton. Received the award for Best Student Paper.
Compilers are traditionally factorised into a number of separate phases, such as parsing, type checking, code generation, etc. However, there is another potential factorisation that has received comparatively little attention: In this article we focus on the problem of modular compilation, in which the aim is to develop compilers for separate language features independently, which can then be combined as required.
We summarise our progress to date, issues that have arisen, and further work. In this article we develop a more structured approach, based upon initial algebra semantics. An extended article with all the proofs is also available.
The standard approach to proving compiler correctness for concurrent languages requires the Final estonia powerpoint with video of multiple translations into an intermediate process calculus.
We present a simpler approach that avoids the need for such an intermediate language, using a new method that allows us to directly establish a bisimulation between the source and target languages.
We illustrate the technique on two small languages, using the Agda system to present and formally verify our compiler correctness proofs. Journal of Functional Programming, 19 2: It has been used by compiler writers for many years, but the technique is little-known in the wider functional programming community, and has never been described precisely.
We also provide a systematic recipe for its use as an equational reasoning technique for improving the performance of programs, and illustrate the power of this recipe using a range of examples.
Powerpoint slides and an extended article with all the proofs are also available. Modularity and implementation of mathematical operational semantics pdfbibtex Mauro Jaskelioff, Neil Ghani, and Graham Hutton.
Structural operational semantics is a popular technique for specifying the meaning of programs by means of inductive clauses.
One seeks syntactic restrictions on those clauses so that the resulting operational semantics is well-behaved. This approach is simple and concrete but it has some drawbacks.
Turi pioneered a more abstract categorical treatment based upon the idea that operational semantics is essentially a distribution of syntax over behaviour. In this article we take Turi's approach in two new directions. Firstly, we show how to write operational semantics as modular components and how to combine such components to specify complete languages.
Secondly, we show how the categorical nature of Turi's operational semantics makes it ideal for implementation in a functional programming language such as Haskell. Towards a verified implementation of software transactional memory pdfbibtex Liyang Hu and Graham Hutton.
In recent years there has been much interest in the idea of concurrent programming using transactional memory, for example as provided in STM Haskell.
While programmers are provided with a simple high-level model of transactions in terms of a stop-the-world semantics, the low-level implementation is rather more complex, using subtle optimisation techniques to execute multiple concurrent transactions efficiently, which is essential to the viability of the programming model.
In this article, we take the first steps towards a formally verified implementation of transactional memory.
In particular, we present a stripped-down, idealised concurrent language inspired by STM Haskell, and show how a low-level implementation of this language can be justified with respect to a high-level semantics, by means of a compiler and its correctness theorem, mechanically tested using QuickCheck and HPC.
The use of these tools proved to be invaluable in the development of our formalisation.
Pure functional languages support programming with impure effects by exploiting mathematical notions such as monads, applicative functors, and arrows. However, in contrast to the wealth of research on the use of these notions to write effectful programs, there has been comparatively little progress on reasoning about the resulting programs.
In this article we focus on this problem, using a simple but instructive example concerned with relabelling binary trees.The Digital Single Market strategy aims to open up digital opportunities for people and business and enhance Europe's position as a world leader in the digital economy.
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