The Syntax and Semantics of Lucid∗

The language Lucid has been developed by the authors over a period of ten years. In that time, the language has undergone many revisions and, even, drastic changes in syntax. As a consequence, all of the published literature on Lucid (for example [2, 3, 1]) does not refer to the current version of the language. With the current version, the language has arrived, finally, at a stable, finished form. (Future changes should only be extensions, and existing programs should remain legal.) A book has been written about this final version [4], and it should appear in late 1984, or early 1985. This paper is concerned with the current language, and will, we hope, encourage the reader to study the book. This paper will give a short description of the syntax and mathematical semantics of Lucid, followed by a discussion of operational ideas appropriate to the language. The first part demonstrates the formal simplicity of the language, and the second part demonstrates the power and expressiveness of the language and the subtlety of its possible operational interpretations. A short final section discusses possible extensions to the language.