Abstract

Space and time problems still occasionally dog the functional programmer, despite increasingly efficient implementations and the recent spate of useful profiling tools. There is a need for a model of program reduction that relates directly to the user's code and has a simple graphical representation. Nave graph reduction provides this. We address the problems of displaying a series of program graphs which may be long, and the elements of which may be large and complex. We offer a scheme for compacting an individual display by creating a quotient graph through defining equivalence classes, and a similar scheme for reducing the number of graphs to show. A metalanguage to allow the user to define compaction rules gives the model flexibility. A prototype system exists in a Haskell implementation. 1 Motivation People are often unable to predict the behaviour of a lazy functional program. Although the order of reduction is deterministic in a given sequential implementation, it is not intuit...

Citations