Adding traces to a lazy monadic evaluator

The debugging of lazy functional programs is a non yet satisfactorily solved problem. In recent years there have been several proposals for incorporating execution traces to lazy functional languages. In [CRW00], an extensive comparison of three of these systems can be found, namely Freja [NS97,Nil98], the Redex Trail System (RTS) [SR97a,SR97b] and Hood [Gil00]. They have been incorporated to different Haskell [JH99] compilers. Freja i