Peter John Landin was a British computer scientist born on June 5, 1930, and he passed away on June 3, 2009. He was among the first people to recognize that the lambda calculus could be used to help create a programming language. This idea was important for the development of functional programming and denotational semantics.

Academic

Peter Landin was born in Sheffield, where he studied at King Edward VII School. He earned his mathematics degree from Clare College, Cambridge, completing it in two years. He then tried to finish a more difficult part of the program but received a third-class degree. From 1960 to 1964, he worked as an assistant to Christopher Strachey, who was a computer consultant in London. Most of his research and writings were published during this time, as well as during his short work at Univac and the Massachusetts Institute of Technology in the United States. Later, he joined Queen Mary University of London.

In the 1970s and 1980s, he helped create the computer science department at Queen Mary College. He designed courses and taught students, as described in the introduction of the textbook Programming from First Principles. After retiring, he was named Emeritus Professor of Theoretical Computation at Queen Mary University of London. In 2012, the university renamed its computer science building the Peter Landin Building in his honor.

At a workshop in London’s Science Museum in 2001, Landin discussed how his career in computer science began in the late 1950s. He said he was influenced by studying John McCarthy’s Lisp language, even though Fortran was the most widely used language at the time.

Landin played a role in developing the ALGOL programming language. He attended the November 1959 conference in Paris and the 1962 conference. Tony Hoare mentioned that Landin helped teach him ALGOL 60, which allowed Hoare to write powerful recursive algorithms.

Landin was involved in setting international standards for programming and informatics. He was a member of IFIP Working Group 2.1, which worked on programming languages like ALGOL 60 and ALGOL 68.

Landin invented several important tools in computer science, including the SECD machine, the first abstract machine for functional programming, and the ISWIM programming language. He also created the Landin off-side rule, which uses spaces to define code structure in languages like Miranda, Haskell, Python, and F#. He introduced the term “syntactic sugar” to describe simple language features that make programming easier.

A phrase from Landin’s paper The next 700 programming languages became famous. He titled it after a number he saw in the Journal of the ACM, which mentioned there were already 700 programming languages. The paper began with the line: “Today… 1,700 special programming languages are used to ‘communicate’ in over 700 application areas.” It also included a joke referencing his earlier work. Landin often used dry humor in his writings.

Political

Landin, who identified as bisexual, joined the Gay Liberation Front (GLF) in the early 1970s. He was arrested during an anti-nuclear protest. He enjoyed cycling and used his bike to travel around London until his physical health made it no longer possible.

Legacy

The Bodleian Library in Oxford has a collection of materials about Peter Landin. Since 2010, an annual Peter Landin Semantics Seminar has been held every December. This event is organized by the BCS-FACS Specialist Group on Formal Aspects of Computing Science. The first seminar was given by American computer scientist John C. Reynolds (1935–2013). Queen Mary University of London has a building named after Peter Landin. This building includes spaces for teaching and research in computer science.

Selected publications

• Landin, Peter J. (1964). "The mechanical evaluation of expressions." The Computer Journal. 6 (4). British Computer Society: 308–320. doi: 10.1093/comjnl/6.4.308.
• Landin, Peter J. (February 1965a). "Correspondence between ALGOL 60 and Church's Lambda-notation: part I." Communications of the ACM. 8 (2). Association for Computing Machinery: 89–101. doi: 10.1145/363744.363749. S2CID 6505810.
• Landin, Peter J. (March 1965b). "A correspondence between ALGOL 60 and Church's Lambda-notation: part II." Communications of the ACM. 8 (3). Association for Computing Machinery: 158–165. doi: 10.1145/363791.363804. S2CID 15781851.
• Landin, Peter J. (29 August 1965c). "A Generalization of Jumps and Labels." UNIVAC Systems Programming Research (Technical Report). Reprinted in Landin, Peter J. (December 1998). "A Generalization of Jumps and Labels." Higher-Order and Symbolic Computation. 11 (2): 125–143. doi: 10.1023/A:1010068630801. S2CID 5579841.
• Landin, Peter J. (1966a). Steel, T. B. Jr. (ed.). "A formal description of Algol 60." Formal Language Description Languages for Computer Programming: 266–294.
• Landin, Peter J. (March 1966b). "The next 700 programming languages." Communications of the ACM. 9 (3). Association for Computing Machinery: 157–166. doi: 10.1145/365230.365257. S2CID 13409665.