Plotkin, in his seminal article Call-by-name, call-by-value and the λ-calculus, formalized evaluation strategies and simulations using operational semantics and continuations. In particular, he showed how call-by-name evaluation could be simulated under call-by-value evaluation and vice versa. Since Algol 60, however, call-by-name is both implemented and simulated with thunks rather than with continuations. We recast

Abstract. To introduce the republication of “Definitional Interpreters for Higher-Order Programming Languages”, the author recounts the circumstances of its creation, clarifies several obscurities, corrects a few mistakes, and briefly summarizes some more recent developments.

We define a partial continuation as the difference of two continuations. We exhibit, in a single framework, several design choices and their impact on semantics. The ability of partial continuations to manipulate stack frames blurs the nature of dynamic extent; therefore, we introduce a new concept of prefixal extent that characterises the time during which a partial continuation can be reified. We propose two equivalent formal semantics for partial continuations: a context-rewriting system and a cps translation. Two new and realistic examples illustrate both the interest of partial continuations and the expressiveness of our choices.

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have severe resource constraints in terms of energy, processing power and memory. In order to work e#ciently within the constrained memory, many operating systems for such devices are based on an event-driven model rather than on multi-threading. While event-driven systems allow for reduced memory usage, they require programs to be developed as explicit state machines. Since implementing programs as explicit state machines is hard, developing, maintaining, and debugging programs for event-driven systems is di#cult.

... decade has led to an increasingly nomadic computing lifestyle. A computer is no longer an immobile, gargantuan machine that remains in one place for the lifetime of its operation. Today's personal computing devices are portable, and Internet access is becoming ubiquitous. A well-traveled laptop user might use half a dozen different networks throughout the course of a day: a cable modem from home, wide-area wireless on the commute, wired Ethernet at the office, a Bluetooth network in the car, and a wireless, local-area network at the airport or the neighborhood coffee shop. Mobile host

Abstract. We present a novel transformation method that allows us to map unstructured cyclic business process models to functionally equivalent workflow specifications that support structured cycles only. Our solution is based on a continuation semantics, which we developed for the graphical representation of a process model. By using a rule-based transformation method originally developed in compiler theory, we can untangle the unstructured flow while solving a set of abstract continuation equations. The generated workflow code can be optimized by controlling the order in which the transformation rules are applied. We then present an implementation of the transformation method that directly manipulates an object-oriented model of the Business Process Execution Language for Web Services BPEL4WS. The implementation maps abstract continuation equations to the BPEL4WS control-flow graph. The transformation rules manipulate the links in the graph such that all cycles are removed and replaced by equivalent structured activities. A byproduct of this work is that, if a continuation semantics is adopted for BPEL4WS, its restriction to acyclic links can be dropped. 1

Compilers for higher-order programming languages like Scheme, ML, and Lisp can be broadly characterized as either "direct compilers" or "continuation-passing style (CPS) compilers", depending on their main intermediate representation. Our central result is a precise correspondence between the two compilation strategies. Starting from

. This note introduces Peter Landin's 1965 technical report "A Generalization of Jumps and Labels", which is reprinted in this volume. Its aim is to make that historic paper more accessible to the reader and to help reading it in context. To this end, we explain Landin's control operator J in more contemporary terms, and we recall Burge's solution to a technical problem in Landin's original account. Keywords: J-operator, secd-machine, call/cc, goto, history of programming languages 1. Introduction In the mid-1960's, Peter Landin was exploring functional programming extended with control. Initially, Landin had added the control operator J (for jump) to his language of Applicative Expressions in order to explicate the goto statement from Algol 60 [10]. This general control construct, however, was powerful enough to have independent interest quite beyond the application to Algol: Landin wrote a series of technical reports [11, 12, 13] on functional programming with control, the most si...

Numerous high-level control operators, with various properties, exist in the literature. To understand or compare them is difficult since their definitions use quite different theoretical frameworks; moreover, to our knowledge, no implementation offers them all. This paper tries to explain control operators by the often simple stack manipulation they perform. We therefore present what we think these operators are, in an executable framework derived from abstract continuations. This library is published in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. For instance, we do not claim our implementation to be faithful nor we attempt to formally derive these implementations from their original definitions. The goal is to give a flavor of what control operators are, from an implementation point of view. Last but worth to say, all errors are mine. Among the many existing control operators, w...