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Documents authored by McCusker, Guy


Document
The Functional Machine Calculus II: Semantics

Authors: Chris Barrett, Willem Heijltjes, and Guy McCusker

Published in: LIPIcs, Volume 252, 31st EACSL Annual Conference on Computer Science Logic (CSL 2023)


Abstract
The Functional Machine Calculus (FMC), recently introduced by the second author, is a generalization of the lambda-calculus which may faithfully encode the effects of higher-order mutable store, I/O and probabilistic/non-deterministic input. Significantly, it remains confluent and can be simply typed in the presence of these effects. In this paper, we explore the denotational semantics of the FMC. We have three main contributions: first, we argue that its syntax - in which both effects and lambda-calculus are realised using the same syntactic constructs - is semantically natural, corresponding closely to the structure of a Scott-style domain theoretic semantics. Second, we show that simple types confer strong normalization by extending Gandy’s proof for the lambda-calculus, including a small simplification of the technique. Finally, we show that the typed FMC (without considering the specifics of encoded effects), modulo an appropriate equational theory, is a complete language for Cartesian closed categories.

Cite as

Chris Barrett, Willem Heijltjes, and Guy McCusker. The Functional Machine Calculus II: Semantics. In 31st EACSL Annual Conference on Computer Science Logic (CSL 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 252, pp. 10:1-10:18, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2023)


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@InProceedings{barrett_et_al:LIPIcs.CSL.2023.10,
  author =	{Barrett, Chris and Heijltjes, Willem and McCusker, Guy},
  title =	{{The Functional Machine Calculus II: Semantics}},
  booktitle =	{31st EACSL Annual Conference on Computer Science Logic (CSL 2023)},
  pages =	{10:1--10:18},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-264-8},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{252},
  editor =	{Klin, Bartek and Pimentel, Elaine},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CSL.2023.10},
  URN =		{urn:nbn:de:0030-drops-174716},
  doi =		{10.4230/LIPIcs.CSL.2023.10},
  annote =	{Keywords: lambda-calculus, computational effects, denotational semantics, strong normalization}
}
Document
On Compositionality of Dinatural Transformations

Authors: Guy McCusker and Alessio Santamaria

Published in: LIPIcs, Volume 119, 27th EACSL Annual Conference on Computer Science Logic (CSL 2018)


Abstract
Natural transformations are ubiquitous in mathematics, logic and computer science. For operations of mixed variance, such as currying and evaluation in the lambda-calculus, Eilenberg and Kelly's notion of extranatural transformation, and often the even more general dinatural transformation, is required. Unfortunately dinaturals are not closed under composition except in special circumstances. This paper presents a new sufficient condition for composability. We propose a generalised notion of dinatural transformation in many variables, and extend the Eilenberg-Kelly account of composition for extranaturals to these transformations. Our main result is that a composition of dinatural transformations which creates no cyclic connections between arguments yields a dinatural transformation. We also extend the classical notion of horizontal composition to our generalized dinaturals and demonstrate that it is associative and has identities.

Cite as

Guy McCusker and Alessio Santamaria. On Compositionality of Dinatural Transformations. In 27th EACSL Annual Conference on Computer Science Logic (CSL 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 119, pp. 33:1-33:22, Schloss Dagstuhl - Leibniz-Zentrum für Informatik (2018)


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@InProceedings{mccusker_et_al:LIPIcs.CSL.2018.33,
  author =	{McCusker, Guy and Santamaria, Alessio},
  title =	{{On Compositionality of Dinatural Transformations}},
  booktitle =	{27th EACSL Annual Conference on Computer Science Logic (CSL 2018)},
  pages =	{33:1--33:22},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-088-0},
  ISSN =	{1868-8969},
  year =	{2018},
  volume =	{119},
  editor =	{Ghica, Dan R. and Jung, Achim},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CSL.2018.33},
  URN =		{urn:nbn:de:0030-drops-97006},
  doi =		{10.4230/LIPIcs.CSL.2018.33},
  annote =	{Keywords: Dinatural transformation, categorical logic, compositionality}
}
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