Abstract. This paper presents a polymorphic type system for a language with delimited control operators, shift and reset. Based on the monomorphic type system by Danvy and Filinski, the proposed type system allows pure expressions to be polymorphic. Thanks to the explicit presence of answer types, our type system satisfies various important properties, including strong type soundness, existence of principal types and an inference algorithm, and strong normalization. Relationship to CPS translation as well as extensions to impredicative polymorphism are also discussed. These technical results establish the foundation of polymorphic delimited continuations.

Abstract. We study the dynamic control operators for delimited continuations, control and prompt. Based on recent developments on purely functional CPS translations for them, we introduce a polymorphically typed calculus for these control operators which allows answer-type modification. We show that our calculus enjoys type soundness and is compatible with the CPS translation. We also show that the typed dynamic control operators can macro-express the typed static ones (shift and reset), while the converse direction is not possible, which exhibits a sharp contrast with the type-free case.

Parsers and pretty-printers for a language are often quite similar, yet both are typically implemented separately, leading to redundancy and potential inconsistency. We propose a new interface of syntactic descriptions, with which both parser and pretty-printer can be described as a single program. Whether a syntactic description is used as a parser or as a pretty-printer is determined by the implementation of the interface. Syntactic descriptions enable programmers syntax once and for all, and use these descriptions for parsing or pretty-printing as needed. We also discuss the generalization of our programming technique towards an algebra of partial isomorphisms.

Abstract. The notion of delimited continuations has been proved useful in various areas of computer programming such as partial evaluation, mobile computing, and web transaction. In our previous work, we proposed polymorphic calculi with control operators for delimited continuations. This paper presents a proof of strong normalization (SN) of these calculi based on a refined (i.e. administrative redex-free) CPS translation.

We study the control operators ”control” and ”prompt” which manage part of continuations, that is, delimited continuations. They are similar to the well-known control operators ”shift” and ”reset”, but differ in that the former is dynamic, while the latter is static. In this paper, we introduce a static type system for ”control ” and ”prompt” which does not use recursive types. We design our type system based on the dynamic CPS transformation recently proposed by Biernacki, Danvy and Millikin. We also introduce let-polymorphism into our type system, and show that our type system satisfies several important properties such as strong type soundness.

This paper reports on the ongoing work to extend type-directed partial evaluation (TDPE) to cope with delimited-control operators, shift and reset. By examining call-by-value TDPE of CPS expressions and transforming it back to direct style, we obtain call-by-value TDPE for shift and reset. The preliminary experiments show that the printf function written with shift and reset has been successfully partially evaluated. 1