Representing Control in the Presence of One-Shot Continuations

Abstract

Traditional first-class continuation mechanisms allow a captured continuation to be invoked multiple times. Many continuations, however, are invoked only once. This paper introduces one-shot continuations, shows how they interact with traditional multi-shot continuations, and describes a stack-based implementation of control that handles both one-shot and multi-shot continuations. The implementation eliminates the copying overhead for one-shot continuations that is inherent in multi-shot continuations. 1 Introduction Scheme [5] and some implementations of ML [17] provide continuations as first-class data objects. Continuations can be used to implement, at the source level, a number of interesting control features, such as loops, nonlocal exits, nonblind backtracking [22], nondeterministic computations [10, 14], and coroutines [7]. Source-level implementations of thread systems [9, 15, 21], especially in the area of graphical user interfaces (GUIs) [12, 13, 20, 23], are an important ...