A Logical Framework for the Algorithmic Debugging of Lazy Functional-Logic Program

Traditional debugging techniques are not well suited for lazy functional programming, because of the diicult-to-predict evaluation order. Therefore, declarative debugging techniques have been proposed, which allow to focus on the intended meaning of programs, abstracting away operational concerns. Similar techniques are known also for logic programming and for combined functional logic languages. The aim of this paper is to provide theoretical foundations for the declarative debug-ging of wrong answers in lazy functional logic programming. We propose a logical framework which formalizes both the intended meaning and the execution model of programs in a simple language which combines the expressivity of pure Prolog and a signiicant subset of Haskell. As a novelty w.r.t. previous related works, we obtain a completely formal speciication of the debugging method. In particular, we extend known soundness and completeness results for the debugging of wrong answers in logic programming to a substantially more diicult context. This work should serve as a clear guideline for a future prototype implementation of a debugging system.