Abstract

Abstract. The phrase \optimal program specialization " was de ned by Jones et al. in 1993 to capture the idea of a specializer being strong enough to remove entire layers of interpretation. As it has become clear that it does not imply \optimality " in the everyday meaning of the word, we propose to rename the concept \Jones-optimality". We argue that the 1993 de nition of Jones-optimality is in principle impossible to ful l for strongly typed languages due to necessary encodings on the inputs and outputs of a well-typed self-interpreter. We propose a technical correction of the de nition which allows Jones-optimality to remain a meaningful concept for typed languages. We extend recent work by Hughes and by Taha and Makholm on the long-unsolved problem of Jones-optimal specialization for strongly typed languages. The methods of Taha and Makholm are enhanced to allow \almost optimal " results when a self-interpreter is specialized to a typeincorrect program; how to do this has been an open problem since 1987. Neither Hughes ' nor Taha{Makholm's methods are by themselves su-cient for Jones-optimal specialization when the language contains primitive operations that produce or consume complex data types. A simple postprocess is proposed to solve the problem. An implementation of the proposed techniques has been produced and used for the rst successful practical experiments with truly Jones-optimal specialization for strongly typed languages.

Citations

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