It is well known that confluence and strong normalization are preserved when combining algebraic rewriting systems with the simply typed lambda calculus. It is equally well known that confluence fails when adding either the usual contraction rule for #, or recursion together with the usual contraction rule for surjective pairing. We show that confluence and strong normalization are modular properties for the combination of algebraic rewriting systems with typed lambda calculi enriched with expansive extensional rules for # and surjective pairing. We also show how to preserve confluence in a modular way when adding fixpoints to di#erent rewriting systems. This result is also obtained by a simple translation technique allowing to simulate bounded recursion. 1 Introduction Confluence and strong normalization for the combination of lambda calculus and algebraic rewriting systems have been the object of many studies [BT88, JO91, BTG94, HM90], where the modularity of these properties is s...

The extensional version of the simply typed -calculus with product types enriched with layered, wildcard, and product patterns is studied. Extensionality is expressed by the surjective pairing axiom and a generalization of the j-conversion to patterns. Two different confluent reduction systems, called lwp \Gamma! and lw \Gamma! respectively, are obtained by turning the extensional axioms as expansion rules, and then adding some restrictions to these expansions to avoid reduction loops. It is shown that only layered and wildcard patterns are redundant in lw \Gamma!, while product patterns are unnecessary in lwp \Gamma!. Confluence of both reduction systems is proven by the composition of modular properties of the systems' extensional and nonextensional parts. Recursion is also added to both systems by keeping the modularity of the confluence property. 1 Introduction Pattern-matching in function definitions is one of the most popular features of functional languages...