More Church–Rosser Proofs

  • Authors:
  • Tobias Nipkow

  • Affiliations:
  • Institut für Informatik, Technische Universität München, 80290 München, Germany. http://www.in.tum.de/˜nipkow/

  • Venue:
  • Journal of Automated Reasoning
  • Year:
  • 2001

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Abstract

The proofs of the Church–Rosser theorems for β, η, and β ∪ η reduction in untyped λ-calculus are formalized in Isabelle/HOL, an implementation of Higher Order Logic in the generic theorem prover Isabelle. For β-reduction, both the standard proof and Takahashi's are given and compared. All proofs are based on a general theory of commutating relations that supports an almost geometric style of reasoning about confluence diagrams.