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The virtues of eta-expansion

Published online by Cambridge University Press:  07 November 2008

C. Barry Jay
Affiliation:
School of Computing Sciences, University of Technology, Sydney PO Box 123, Broadway 2007Australia (e-mail: cbj@socs.uts.edu.au)
Neil Ghani
Affiliation:
LFCS, Department of Computer Science, University of EdinburghThe King's Buildings, Mayfield Road Edinburgh EH9 3JZ, UK (e-mail: ng@dcs.ed.ac.uk)
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Abstract

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Interpreting η-conversion as an expansion rule in the simply-typed λ-calculus maintains the confluence of reduction in a richer type structure. This use of expansions is supported by categorical models of reduction, where β-contraction, as the local counit, and η-expansion, as the local unit, are linked by local triangle laws. The latter form reduction loops, but strong normalization (to the long βη-normal forms) can be recovered by ‘cutting’ the loops.

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Articles
Copyright
Copyright © Cambridge University Press 1995

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