Higher-Order and Symbolic Computation, 13(1/2)5-6

Editorial

Olivier Danvy and Carolyn Talcott

This issue of HOSC is dedicated to the memory of Christopher Strachey, 25 years after his passing away [2]. It highlights Strachey's contributions, achievements, and inspiration to other researchers in the areas of programming and of programming languages. The issue begins with Strachey's influential lecture notes "Fundamental Concepts in Programming Languages". These lecture notes were written for a summer school held in Copenhagen, Denmark, in 1967 [4], and Strachey revised them the following year. Unfortunately, the proceedings of the summer school were never published, and thus the lecture notes were only circulated privately. It is our privilege to make this valuable resource available at last. Peter Mosses, who was one of Strachey's last PhD students, kindly agreed to write a foreword.

The issue continues with a collection of tributes from students and colleagues of Strachey. We wanted these tributes to provide a primarily scientific historical perspective, but by force of circumstances, this perspective ended up to be personal as well. These tributes reveal an innovator of many important concepts that have become part of the foundations of programming and programming languages; a theoretician and practitioner who treated programming-language design, implementation, and semantics as an integrated whole; and an inspiring teacher and mentor, gifted with an intense and energetic personality. The issue ends with Strachey and Wadsworth's technical monograph on continuations [5]. Christopher Wadsworth (who coined the term `continuation') kindly agreed to write a foreword. It is worth pondering about how, by his own account, Wadsworth invented continuations: the mechanism of this invention vividly illustrates the sudden change of state in a supersaturated medium (namely, the state of his mind after years of efforts to formalize jumps denotationally) at a tiny event (namely, Strachey pronouncing the words "tail functions" when telling him the title of Mazurkiewicz's article "Proving Algorithms by Tail Functions"). As it appears, though, the early 70s were themselves a supersaturated solution with many crystallization loci: continuations were invented in so many kinds of settings that it is more appropriate to follow the mathematical tradition and speak of discovery rather than of invention. We refer the reader to John Reynolds's 1993 article for a comprehensive account of the many discoveries of continuations [3]. As this special issue is going to press, we would like to extend our thanks to a number of people for their assistance. Barbara Strachey Halpern, who was Christopher Strachey's sister and executor, agreed to our proposal to reprint the lecture notes, wishing us well with the project.1 Daniel Damian, Bernd Grobauer, and Karen Møller typeset the lecture notes and the technical monograph. Rod Burstall, Mike Gordon, Gerard Huet, Gilles Kahn, Jean-Jacques Levy, John McCarthy, Lockwood Morris, Peter Mosses, Roger Needham, Jean-Francois Perrot, John Reynolds, Karen Sparck-Jones, Joe Stoy, and Maurice Wilkes answered our queries very helpfully. Maurice Wilkes declined to contribute, referring us to his memoirs for an appreciation of CPL and of Strachey's involvement [6, pp. 227-228]. Daniel Damian, Kent Dybvig, Andrzej Filinski, Bernd Grobauer, Peter Mosses, Lasse Nielsen, John Reynolds, Morten Rhiger, Bob Tennent, David Toman, and Zhe Yang proofread various parts of this special issue. Thanks are also due to all the contributors for bearing with our editorial requests and tight deadlines.2

Notes

1. Her obituary, available at http://www.the-times.co.uk (click on "Library" and then request 17 November 1999), seems to echo Dana Scott's words "a strong woman from a line of strong women."

2. In fact, our deadlines proved so tight that they prevented David Barron [1] to contribute to this special issue. However, he kindly authorized us to reproduce the following dedication of his forthcoming book on programming-language history.

"Dedicated to the memory of Christopher Strachey (1916-1975). Although he denied the existence of Computer Science as an academic discipline, he will be remembered as one of its founding fathers. He introduced me to the study of programming languages, and had all the good ideas first."

References

1. Barron, D. Home page. http://www.ecs.soton.ac.uk/~dwb/.

2. Campbell-Kelly, M. Christopher Strachey, 1916-1975, A Biographical Note. Annals of the History of Computing 7(1) (1985) 19-42.

3. Reynolds, J.C. The discoveries of continuations. Lisp and Symbolic Computation 6(3/4) (1993) 233-247.

4. Strachey, C. Fundamental concepts in programming languages. In Proceedings of the 1967 International Summer School in Computer Programming, Copenhagen, Denmark, 1967. Unpublished.

5. Strachey, C. and Wadsworth, C.P. Continuations: A mathematical semantics for handling full jumps. Technical Monograph PRG-11, Oxford University Computing Laboratory, Programming Research Group, Oxford, England, 1974.

6. Wilkes, M.V. Memoirs of a Computer Pioneer. The MIT Press, 1985.

June 2003 - hosc@brics.dk