Gergely Dévai

Feldspar: A domain specific language for digital signal processing algorithms

A new language, Feldspar, is presented, enabling high-level and platform-independent description of digital signal processing (DSP) algorithms. Feldspar is a pure functional language embedded in Haskell. It offers a high-level dataflow style of programming, as well as a more mathematical style based on vector indices. The key to generating efficient code from such descriptions is a high-level optimization technique called vector fusion. Feldspar is based on a low-level, functional core language which has a relatively small semantic gap to machine-oriented languages like C. The core language serves as the interface to the back-end code generator, which produces C. For very small examples, the generated code performs comparably to hand-written C code when run on a DSP target. While initial results are promising, to achieve good performance on larger examples, issues related to memory access patterns and array copying will have to be addressed.

An Introduction to the Lambda Calculus

Lambda calculus (?-calculus) is one of the most well-known formal models of computer science. It is the basis for functional programming like Turing machines are the foundation of imperative programming. These two systems are equivalent and both can be used to formulate and investigate fundamental questions about solvability and computability. First, we introduce the reader to the basics of ?-calculus: its syntax and transformation rules. We discuss the most important properties of the system related to normal forms of ?-expressions. We present the recursive version of ?-calculus and finally give the classical results that establish the link between ?-calculus, partial recursive functions and Turing machines.

Textual diagram layout language and visualization algorithm

Graphical diagrams are an excellent source of information for understanding models. On the other hand, editing, storing and versioning models are more efficient in textual representations. In order to combine the advantages of these two representations, diagrams have to be generated from models defined in text. The generated diagrams are usually created by autolayout algorithms based on heuristics. In this paper we argue that automatically laid out diagrams are not ideal. Instead, we propose a textual layout description language that allows users to define the arrangement of those diagram elements they consider important. The paper also presents algorithms that create diagrams according to the layout description and arrange the underspecified elements automatically. The paper reports on the implementation of the proposed layout description language as an embedded language in Java. It is used to generate class and state machine diagrams compatible with the Papyrus UML editor.

Embedding a proof system in haskell

This article reports about a work-in-progress project that aims at embedding a proof system [4] in the Haskell programming language. The goal of the system is to create formally verified software using the correctness by construction principle. Using Haskell as the host language provides a powerful and flexible environment so that programming language tools can be used to build proofs. The main contribution of this paper is the systematic analysis of different techniques for language embedding. We present design decisions by pointing out which techniques are applicable and which ones are inappropriate or inconvenient to use when embedding a proof system like the our one. We also point out the advantages of the embedding compared to a previous implementation of the same system.

Language Design and Implementation via the Combination of Embedding and Parsing

Language embedding is a method to implement a new language within the framework of an existing programming language. This method is known to speed up the development process compared to standalone languages using classical compiler technology. On the other hand, embedded languages may not be that convenient for the end-users as standalone ones with own concrete syntax. This paper describes a method that uses the flexibility of language embedding in the experimental phase of the language design process, then, once the language features are mature enough, adds concrete syntax and turns the language to a standalone one. Lessons learnt from a project, run in industry-university cooperation and using the presented method, are discussed. Based on these results, a cost model is established that can be used to estimate the potential benefits of this method in case of future language design projects.

The EDSL’s Struggle for Their Sources

Embedded Domain Specific Languages make language design and implementation easier, because lexical and syntactical analysis and part of the semantic checks can be completed by the compiler of the host language.