Intersection Types and Termination Properties

  • Authors:
  • George Koletsos

  • Affiliations:
  • National Technical University of Athens, Department of Computer Science, Zografou Campus-157 80 Athens-Greece. koletsos@math.ntua.gr

  • Venue:
  • Fundamenta Informaticae - Intersection Types and Related Systems ITRS
  • Year:
  • 2012

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Abstract

We use the system of intersection types and the type assignment method to prove termination properties in λ-calculus. In the first part we deal with conservation properties. We give a type assignment proof of the classical conservation theorem for λI calculus and then we extend this method to the notion of the reduction βI and βS of de Groote [9]. We also give a direct type assignment proof of the extended conservation property according to which if a term is βI, βS-normalizable then it is β-strongly normalizable. We further extend the conservation theorem by introducing the notion of β*-normal form. In the second part we prove that if Ω is not a substring of a λ-term M then M can be typed in the Krivine's system D of intersection types. In that way we obtain a type assignment proof of the Sørensen's Ω-theorem.