Abstract

. Redex trails are histories of functional computations by graph reduction; their main application is fault-tracing. A prototype implementation of a tracer based on redex trails [8] demonstrated the promise of the technique, but was limited in two respects: (1) trails did not record every reduction, only those constructing a new value; (2) even so computing trails was very expensive, particularly in terms of the memory space they occupied. In this paper, we address both problems: complete redex trails provide a full computational record; partial versions of these trails exclude all but selected details, greatly reducing memory costs. We include results of experiments tracing several applications, including a compiler. 1 Introduction Programs do not always work first time. When they fail, programmers cannot always see the reason immediately. Implementors must therefore provide some way of tracing computations. By examining traces, programmers can see not only final results o...

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