Maintaining Dynamic State: Deep, Shallow, and Parallel

In the presence of rst-class continuations, shallow maintenance of dynamic bindings requires more than the traditional stack-based techniques. This paper provides correctness criteria for such dynamic environments, along with contrasting implementations. A store semantics provides the framework for our correctness criteria and presentation of deepand shallow-binding implementations. The latter implementation is a new state-space algorithm, which is proved correct. A variation of the algorithm implements Scheme's dynamic-wind operation. Finally, a technique for maintaining dynamic state called semi-shallow binding is presented. This compromise between deepand shallow-binding appears suitable for parallel systems. Applications include uid binding of lexical variables and logic programming with rst-class continuations.