Inspired by recent work on normalisation by evaluation for sums, we propose a normalising and confluent extensional rewriting theory for the simply-typed λ-calculus extended with sum types. As a corollary of confluence we obtain decidability for the extensional equational theory of simply-typed λ-calculus extended with sum types. Unlike previous decidability results, which rely on advanced rewriting techniques or advanced category theory, we only use standard techniques.


Normal Form Equational Theory Parallel Case Type Constructor Strong Normalisation 
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© Springer Berlin Heidelberg 2007

Authors and Affiliations

  • Sam Lindley
    • 1
  1. 1.Laboratory for Foundations of Computer Science, School of Informatics, The University of Edinburgh 

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