Note: The first version of this paper was submitted for publication in the last millennium. Successive versions have spent many years with reviewers, plus I have taken substantial time revising technical and sylistic aspects, out-staying the terms of several editors and even a journal. For years the paper seemed well and truly floundered. But finally it has been transformed into success, accepted to appear in Theory and Practice of Logic Programming (TPLP).
Keywords: Floundering, delays, coroutining, program analysis, abstract interpretation, program transformation, declarative debugging