A semi-reflexive tactic for (sub-)equational reasoning

  • Authors:
  • Claudio Sacerdoti Coen

  • Affiliations:
  • Project PCRI, CNRS, École Polytechnique, INRIA, Université Paris-Sud

  • Venue:
  • TYPES'04 Proceedings of the 2004 international conference on Types for Proofs and Programs
  • Year:
  • 2004

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Abstract

We propose a simple theory of monotone functions that is the basis for the implementation of a tactic that generalises one step conditional rewriting by “propagating” constraints of the form xRy where the relation R can be weaker than an equivalence relation. The constraints can be propagated only in goals whose conclusion is a syntactic composition of n-ary functions that are monotone in each argument. The tactic has been implemented in the Coq system as a semi-reflexive tactic, which represents a novelty and an improvement over an earlier similar development for NuPRL. A few interesting applications of the tactic are: reasoning in type theory about equivalence classes (by performing rewriting in well-defined goals); reasoning about reductions and properties preserved by reductions; reasoning about partial functions over equivalence classes (by performing rewriting in PERs); propagating inequalities by replacing a term with a smaller (greater) one in a given monotone context.