This paper describes the language Lustre, which is a dataflow synchronous language, designed for programming reactive systems --- such as automatic control and monitoring systems --- as well as for describing hardware. The dataflow aspect of Lustre makes it very close to usual description tools in these domains (block-diagrams, networks of operators, dynamical samples-systems, etc: : : ), and its synchronous interpretation makes it well suited for handling time in programs. Moreover, this synchronous interpretation allows it to be compiled into an efficient sequential program. Finally, the Lustre formalism is very similar to temporal logics. This allows the language to be used for both writing programs and expressing program properties, which results in an original program verification methodology. 1 Introduction Reactive systems Reactive systems have been defined as computing systems which continuously interact with a given physical environment, when this environment is unable to sy...

Synchronous dataflow languages such as Lustre and Signal have been proposed as a tool for programming reactive systems. These languages rely on a clock analysis to ensure that synchronous operations receive their arguments at the same time. We present a denotational model of a Lustre-like dataflow language and show how a range of clock analyses for this language can be designed and proved correct. To the best of our knowledge this is the first formal correctness proof for such an analysis. We then give a type system formulation of this analysis using clocks as types and show how adding polymorphic clocks enables us to treat programs where clocks vary according to their context. The relationship to the clock analysis by constraint solving used in the language Signal is discussed. 1 Introduction One of the earliest models of concurrent computation is Kahn's networks of processes [Kah74, KM77]. Such a network consists of a set of deterministic processes, or agents, communicating in an ...

This document is an introduction to the language Lustre V4 and its associated tools. We will not give a systematic presentation of the language, but a complete bibliography is added. The basic references are [8, 12]. The most recent features (arrays, recursive nodes) are described in [32]

81/2 is a data-parallel language that relies on the notions of stream and collection in a high-level declarative framework. We describe in this research report semantics and compilation of sequential streams of collections for this language. Firstly, a denotational semantics is associated with recursively defined sequential 81/2 streams. Furthermore, we explain how the fixed point calculus corresponding to the foregoing semantics is implemented. Secondly, we describe an effective code generation scheme targetted towards either sequential, vector or SIMD architectures. Then we present four optimization processes for the generated code: the sharing of common control expressions, the optimization of delay copies, the loop fusion and the concatenation optimization. Next, some elements for the evaluation of the generated code are given. As a conclusion, we recall the overall effectiveness of the stream compilation and draw the future work. Key-words: stream, compilation of data-flow graphs...

Recursive definition of streams (infinite lists of values) have been proposed as a fundamental programming structure in various fields. A problem is to turn such expressive recursive definitions into an efficient imperative code for their evaluation. One of the main approach is to restrict the stream expressions to interpret them as a temporal sequence of values. Such sequential stream rely on a clock analysis to decide at what time a new stream value must be produced. In this paper we present a denotational semantics of recursively defined sequential streams. We show how an efficient implementation can be derived as guarded statements wrapped into a single imperative loop.