We prove that observational equivalence of IA3 + Y0 (3rdorder Idealized Algol with 0th-order recursion) is equivalent to the DPDA Equivalence Problem, and hence decidable. This completes the classification of decidable fragments of Idealized Algol. We also prove that observational approximation of IA1 + Y0 is undecidable by reducing the DPDA Containment Problem to it.

Using game semantics we prove that program equivalence is undecidable in finitary Idealized Algol with active expressions as well as in its call-by-value counterpart. It is also shown that strategies corresponding to Idealized Algol terms of respectively second, third and higher orders define exactly regular, context-free and recursively enumerable languages.

We give a fully abstract game model for Idealized Algol with non-local control flow. In contrast to most previous papers on game semantics, we do not need to include the bad-variable constructor mkvar to obtain full abstraction. Using the model we show that, unlike in the “control-free” case, the presence of mkvar does affect observational equivalence. We conclude by discussing the effect of mk...

The manipulation of objects with state which changes over time is all-pervasive in computing. Perhaps the simplest example of such objects are the program variables of classical imperative languages. An important strand of work within the study of such languages, pioneered by John Reynolds, focusses on \Idealized Algol", an elegant synthesis of imperative and functional features. We present a n...

The manipulation of objects with state which changes over time is all-pervasive in computing. Perhaps the simplest example of such objects are the program variables of classical imperative languages. An important strand of work within the study of such languages, pioneered by John Reynolds, focusses on \Idealized Algol", an elegant synthesis of imperative and functional features. We present a n...

In this paper, we bring together two important ideas in the semantics of Algol-like imperative programming languages. One is that program phrases act on xed sets of storage locations. The second is that the information of local variables is hidden from client programs. This involves combining sheaf theory and parametricity to produce new classes of sheaves. We deene the semantics of an Algol-li...

A six line recursive procedure is used to assess the efficiency of the procedure calling mechanism in ALGOL-like languages. The results from some 40 systems varying from ALGOL 68 and PL/I to System Implementation Languages for minicomputers are presented and compared. A hundred to one variation in performance occurs with this test, the major reasons for which are given. Received April 17, 1975....

The manipulation of objects with state which changes over time is all-pervasive in computing. Perhaps the simplest example of such objects are the program variables of classical imperative languages. An important strand of work within the study of such languages, pioneered by John Reynolds, focuses on \Idealized Algol", an elegant synthesis of imperative and functional features. We present a no...

The facilities of the PS-algol programming language are described in this paper to show how they may be used to provide an integrated programming support environment. The persistent store mechanism and the secure transaction facilities provide the basic environment in which an integrated system may be implemented. In particular the paper makes use of the data type picture of PS-algol to show ho...

[?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?]. Abstraction [?, ?, ?, ?, ?]. Abstractions [?, ?, ?, ?]. abuse [?]. Accelerate [?]. Accelerated [?]. Accelerating [?, ?]. acceleration [?]. Acceptance [?, ?, ?]. Access [?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?]. Access-Control [?]. Accesses [?, ?]. Accessing [?, ?, ?]. accommodate [?]. according [?, ?, ?, ?]. Acc...