Peter Landin

Peter Landin
Born (1930-06-05)5 June 1930
Died 3 June 2009(2009-06-03) (aged 78)
Nationality British
Known for ISWIM, J operator, SECD machine, off-side rule

Peter John Landin (5 June 1930, Sheffield – 3 June 2009[1][2]) was a British computer scientist. He was one of the first to realize that the lambda calculus could be used to model a programming language, an insight that is essential to development of both functional programming and denotational semantics.


Landin was born in Sheffield, where he attended King Edward VII School; he graduated from Clare College, Cambridge University.[2] From 1960 to 1964, he was the assistant to Christopher Strachey when the latter was an independent computer consultant in London. Most of his work was published during this period and the brief time he worked for Univac and at the Massachusetts Institute of Technology in the United States before taking a position at Queen Mary, University of London. During the 1970s and 1980s, his efforts went into building the Computer Science department in Queen Mary College, developing courses and teaching students.[3] On his retirement, he was appointed Emeritus Professor of Theoretical Computation at Queen Mary, University of London, where in 2012 the Computer Science building was renamed the Peter Landin Building in his honour.

At a workshop at the Science Museum, London, in 2001, on the history of programming semantics he spoke of how his scholarly career in computer science began in the late 1950s and of how he was much influenced by a study of McCarthy's LISP when the most commonly used language was Fortran.[4]

He was active in the definition of the ALGOL programming language[5][6] and cited by Tony Hoare as one of the people who taught him ALGOL 60 and hence facilitated his expression of powerful recursive algorithms:

"Around Easter 1961, a course on ALGOL 60 was offered in Brighton, England, with Peter Naur, Edsger W. Dijkstra, and Peter Landin as tutors. ... It was there that I first learned about recursive procedures and saw how to program the sorting method which I had earlier found such difficulty in explaining. It was there that I wrote the procedure, immodestly named QUICKSORT, on which my career as a computer scientist is founded. Due credit must be paid to the genius of the designers of ALGOL 60 who included recursion in their language and enabled me to describe my invention so elegantly to the world. I have regarded it as the highest goal of programming language design to enable good ideas to be elegantly expressed."[7]

Landin is responsible for inventing the SECD machine, the first abstract machine for a functional programming language,[8] and the ISWIM programming language, defining the Landin off-side rule and for coining the term syntactic sugar. The off-side rule allows bounding scope declaration by use of white spaces as seen in languages such as Miranda, Haskell, Python and F# (using the "light" syntax).

Another phrase originating with Landin is "The next 700 ..." after his influential paper The next 700 programming languages.[9] "700" was chosen because Landin had read in the Journal of the ACM that there were already 700 programming languages in existence.[10] The paper opens with the quotation "... today ... 1,700 special programming languages used to 'communicate' in over 700 application areas."[11] It also includes the joke that

A possible first step in the research program is 1700 doctoral theses called "A Correspondence between x and Church's λ-notation."

a reference to his earlier paper.[12] This dry sense of humour is expressed in many of his papers.


Landin, who was bisexual,[2] became involved with the Gay Liberation Front (GLF) during the early 1970s. He was once arrested as part of an anti-nuclear demonstration.[13] He was a dedicated cyclist and moved around London on his bike until it became physically impossible for him to do so.

Selected publications

See also


  1. Peter Landin, Lambda the Ultimate, 4 June 2009.
  2. 1 2 3 Bornat 2009a
  3. Acknowledged in the foreword to the text book Programming from First Principles by Richard Bornat. Published by Prentice Hall, 1987. ISBN 978-0-13-729104-5.
  4. Program Verification and Semantics: Report at the Wayback Machine (archived 26 September 2007), 2001.
  5. Listed amongst those who attended the November 1959 conference in [Paris] and the 1962 conference .
  6. Landin 1964b
  7. ACM Turing Award Lecture: The Emperor's Old Clothes. C. Antony R. Hoare, 1980, Published in the Communications of the ACM.
  8. Stephan Diehl, Pieter Hartel, Peter Sestoft (2000). "Abstract machines for programming language implementation". Future Generation Computer Systems, Volume 16, Issue 7, pages 739–751.
  9. Landin 1966
  10. Personal communication, September 2007.
  11. Computer Software Issues, an American Mathematical Association Prospectus, July 1965.
  12. Landin 1965a
  13. Bornat 2009b

Further reading

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