We give a brief account of the discoveries of continuations and related concepts by, A. Van Wijngaarden , A. W. Mazurkiewicz , F. L. Morris , C. P. Wadsworth , J. H. Morris , M. J. Fischer , and S. K. Abdali.

New tools are presented for reasoning about properties of recursively defined domains. We work within a general, category-theoretic framework for various notions of `relation' on domains and for actions of domain constructors on relations. Freyd's analysis of recursive types in terms of a property of mixed initiality/finality is transferred to a corresponding property of invariant relations. The existence of invariant relations is proved under completeness assumptions about the notion of relation. We show how this leads to simpler proofs of the computational adequacy of denotational semantics for functional programming languages with user-declared datatypes. We show how the initiality/finality property of invariant relations can be specialized to yield an induction principle for admissible subsets of recursively defined domains, generalizing the principle of structural induction for inductively defined sets. We also show how the initiality /finality property gives rise to the co-induct...

. For programming languages whose denotational semantics uses fixed points of domain constructors of mixed variance, proofs of correspondence between operational and denotational semantics (or between two different denotational semantics) often depend upon the existence of relations specified as the fixed point of non-monotonic operators. This paper describes a new approach to constructing such relations which avoids having to delve into the detailed construction of the recursively defined domains themselves. The method is introduced by example, by considering the proof of computational adequacy of a denotational semantics for expression evaluation in a simple, untyped functional programming language. 1 Introduction It is well known that various domain constructors can be extended to act on relations on domains. For example, given binary relations R and S on domains D and E, there is a binary relation R!S on the domain of continuous functions D!E given by: (f; g) 2 (R!S) if and onl...

This paper describes a mixed induction/co-induction property of relations on recursively defined domains. We work within a general framework for relations on domains and for actions of type constructors on relations introduced by O'Hearn and Tennent [20], and draw upon Freyd's analysis [7] of recursive types in terms of a simultaneous initiality/finality property. The utility of the mixed induction/co-induction property is demonstrated by deriving a number of families of proof principles from it. One instance of the relational framework yields a family of induction principles for admissible subsets of general recursively defined domains which extends the principle of structural induction for inductively defined sets. Another instance of the framework yields the co-induction principle studied by the author in [22], by which equalities between elements of recursively defined domains may be proved via `bisimulations'. 1 Introduction A characteristic feature of higher-order functional lan...

This note is a historical survey of Christopher Strachey's influence on the development of semantic models of assignment and storage management in procedural languages.

. In this paper we show that the critical part of a correctness proof for implementations of higher--order functional languages is amenable to machine--assisted proof. An extended version of the lambdacalculus is considered, and the congruence between its direct and continuation semantics is proved. The proof has been constructed with the help of a generic theorem prover --- Isabelle. The major part of the problem lies in establishing the existence of predicates which describe the congruence. This has been solved using Milne's inclusive predicate strategy [5]. The most important intermediate results and the main theorem as derived by Isabelle are quoted in the paper. Keywords: Compiler Correctness, Theorem Prover, Congruence Proof, Denotational Semantics, Lambda Calculus 1 Introduction Much of the work done previously in compiler correctness concerns restricted subsets of imperative languages. Some studies involve machine--checked correctness---e.g. Cohn [1], [2]. A lot of research h...

My early research was inspired by the mathematical semantics of Scott and Strachey. Two such topics, recounted in this paper, were the xed-point analysis of pointer loops and the expressibility of a style of functional programming introduced by Barron and Strachey.

In mathematical semantics, in the sense of Scott, the question arises of what domains of interpretation should be chosen. It has been felt by the author, and others, that lattices are the wrong choice and instead one should use complete partial orders (cpo’s), which do not necessarily have the embarrassing top element. So far, however, no mathematical theory as pleasant as that developed for Pw in the paper “Data Types as Lattices ” has been available. The present paper is intended to fill this gap and is a close analog of the Pw paper, replacing Pw by 8”‘, the w-power of the three-element truthvalue cpo, T. 1.

Abstract. For programming languages whose denotational semantics uses xed points of domain constructors of mixed variance, proofs of correspondence between operational and denotational semantics (or between two di erent denotational semantics) often depend upon the existence of relations speci ed as the xed point of non-monotonic operators. This paper describes a new approach to constructing such relations which avoids having to delve into the detailed construction of the recursively de ned domains themselves. The method is introduced by example, by considering the proof of computational adequacy of a denotational semantics for expression evaluation in a simple, untyped functional programming language. 1