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On the Decidability of Subtyping with Bounded Existential Types

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Book cover Programming Languages and Systems (APLAS 2009)

Part of the book series: Lecture Notes in Computer Science ((LNPSE,volume 5904))

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Abstract

Bounded existential types are a powerful language feature for modeling partial data abstraction and information hiding. However, existentials do not mingle well with subtyping as found in current object-oriented languages: the subtyping relation is already undecidable for very restrictive settings.

This paper considers two subtyping relations defined by extracting the features specific to existentials from current language proposals (JavaGI, WildFJ, and Scala) and shows that both subtyping relations are undecidable. One of the two subtyping relations remains undecidable even if bounded existential types are removed.

With the goal of regaining decidable type checking for the JavaGI language, the paper also discusses various restrictions including the elimination of bounded existentials from the language as well as possible amendments to regain some of their features.

A preliminary version of this work was presented at FTfJP 2008 [24].

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Authors and Affiliations

  1. Institut für Informatik, Universität Freiburg,  

    Stefan Wehr & Peter Thiemann

Authors
  1. Stefan Wehr
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  2. Peter Thiemann
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Editors and Affiliations

  1. National Institute of Informatics (NII), Information Systems Architecture REsearch Division, 2-1-2 Hitotsubashi, Chiyoda-ku, 101-8430, Tokyo, Japan

    Zhenjiang Hu

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Wehr, S., Thiemann, P. (2009). On the Decidability of Subtyping with Bounded Existential Types. In: Hu, Z. (eds) Programming Languages and Systems. APLAS 2009. Lecture Notes in Computer Science, vol 5904. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-10672-9_10

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  • DOI: https://doi.org/10.1007/978-3-642-10672-9_10

  • Publisher Name: Springer, Berlin, Heidelberg

  • Print ISBN: 978-3-642-10671-2

  • Online ISBN: 978-3-642-10672-9

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