A Logical Framework with Explicit Conversions

  • Authors:
  • Herman Geuvers;Freek Wiedijk

  • Affiliations:
  • Department of Computer Science, University of Nijmegen, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands;Department of Computer Science, University of Nijmegen, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands

  • Venue:
  • Electronic Notes in Theoretical Computer Science (ENTCS)
  • Year:
  • 2008

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Abstract

The type theory @lP corresponds to the logical framework LF. In this paper we present @lH, a variant of @lP where convertibility is not implemented by means of the customary conversion rule, but instead type conversions are made explicit in the terms. This means that the time to type check a @lH term is proportional to the size of the term itself. We define an erasure map from @lH to @lP, and show that through this map the type theory @lH corresponds exactly to @lP: any @lH judgment will be erased to a @lP judgment, and conversely each @lP judgment can be lifted to a @lH judgment. We also show a version of subject reduction: if two @lH terms are provably convertible then their types are also provably convertible.