Strong Normalization and Equi-(Co)Inductive Types

  • Andreas Abel
Part of the Lecture Notes in Computer Science book series (LNCS, volume 4583)


A type system for the lambda-calculus enriched with recursive and corecursive functions over equi-inductive and -coinductive types is presented in which all well-typed programs are strongly normalizing. The choice of equi-inductive types, instead of the more common iso-inductive types, influences both reduction rules and the strong normalization proof. By embedding iso- into equi-types, the latter ones are recognized as more fundamental. A model based on orthogonality is constructed where a semantical type corresponds to a set of observations, and soundness of the type system is proven.


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© Springer Berlin Heidelberg 2007

Authors and Affiliations

  • Andreas Abel
    • 1
  1. 1.Department of Computer Science, University of Munich, Oettingenstr.67, D-80538 MünchenGermany

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