A declarative debugger of incorrect answers for constraint functional-logic programs

Debugging is one of the essential parts of the software development cycle. However, the usual debugging techniques used in imperative languages such as the step by step execution often are not suitable for debugging declarative programming languages. We present here a graphical debugging environment for constraint lazy functional-logic programs based on declarative debugging. The debugger displays the computation tree associated with a computation which has produced an incorrect answer, and navigates it with the assistance of the user until the error, an incorrect program rule, is found out. The debugger supports programs including equality and disequality constraints.