Replacing Unevaluated Parts in the Traces of Functional Programs

In functional programming languages such as Haskell, it happens often that some parts of a program are not evaluated because their values are not demanded. In practice, those unevaluated parts are often replaced by a placeholder (e.g. ₎ in order to keep the trace size smaller. For algorithmic debugging, this also makes the questions shorter and clearer. In this paper, we present a formal model of tracing in which unevaluated parts are replaced by the symbol _. Some properties such as the correctness of algorithmic debugging will also be proved.