In the section on "challenging problems" in the proceedings from the first international workshop on partial evaluation and mixed computation [BEJ88] a question is stated: "Can PE be used to generate new specialized data types, in a way analogous to generating specialized functions". Since then little has been done to address this problem. In [Lau89], new types are indeed generated, but they are all simpler versions of the types in the original program. It is, e.g. not possible to have types with more constructors than the types in the original program. I propose to alleviate this by means of constructor specialization. Constructors are specialized with respect to the static parts of their arguments, just like residual functions. I show how this is done and argue that it makes it possible to get good results from partial evaluation in cases where the traditional methods fail to produce satisfactory results. The discussion is centered around a small subset of Standard ML, but the idea a...

Abstract. We study the evolution of partial evaluators over the past fifteen years from a particular perspective: The attempt to prevent structural bounds in the original programs from imposing limits on the structure of residual programs. It will often be the case that a language allows unbounded numbers or sizes of particular features, but each program (being finite) will only have a finite number or size of these features. If the residual programs cannot overcome the bounds given in the original program, that can be seen as a weakness in the partial evaluator, as it potentially limits the effectiveness of residual programs. We show how historical developments in partial evaluators have removed inherited limits, and suggest how this principle can be used as a guideline for further development. 1

Abstract. We show the evolution of partial evaluators over the past ten years from a particular perspective: the attempt to remove limits on the structure of residual programs that are inherited from structural bounds in the original programs. It will often be the case that a language allows an unbounded number or size of a particular features, but each program (being nite) will only have a nite number or size of these features. If the residual programs cannot overcome the bounds given in the original program, that can be seen as a weakness in the partial evaluator, as it potentially limits the e ectiveness of residual programs. The inherited limits are best observed through specializing a self-interpreter and examining the object programs produced by specialisation of this. We show how historical developments in partial evaluators gradually remove inherited limits, and suggest how this principle can be used as a guideline for further development. 1