Eta Expansions in System
نویسنده
چکیده
The use of expansionary-rewrite rules in various typed-calculi has become increasingly common in recent years as their advantages over contractive-rewrite rules have become apparent. Not only does one obtain the decidability of-equality, but rewrite relations based on expansions give a natural interpretation of long-normal forms, generalise more easily to other type constructors, retain key properties when combined with other rewrite relations, and are supported by a categorical theory of reduction. This paper extends the initial results concerning the simply typed-calculus to System F, that is, we prove strong normalisation and connuence for a rewrite relation consisting of traditional-reductions and-expansions satisfying certain restrictions. Further, we characterise the second order long-normal forms as precisely the normal forms of the restricted rewrite relation. These results are an important step towards showing that-expansions are compatible with the more powerful members of the-cube and also towards a smooth combination of type theories with-equality and algebraic rewrite systems.
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