Adam Wyner
I am getting a "pattern match failure", and then subsequent functions which worked right work wrong. I am using Hugs and Trex.
INTERNAL ERROR: Error in graph it means that the whole internal evaluation context has become corrupted. Any further use of the reduction graph (representing the
The problem with subsequent evaluations is simple. When Hugs says this: program) is likely to give wrong answers. Reloading the program code wipes the internal graph and starts again. Normally, when someone gets an error message (like "pattern-match failure"), they go and fix the program immediately, then reload, which is why few people complain about the cascading-errors behaviour.
Program error: pattern match failure: map_v780 (instEq_v20 instEq_v11 Eq_== "neg-prop2") map_v780
The pattern-match failure seems to be in an expression looking something like map (== "neg-prop2") xs and I think the problem is possibly in an "instance Eq" you have written by hand for one of your datatypes. "Pattern-match failure" means that you have not covered all the possible patterns in your definition. This might either be on the LHS of the defn, or in a case expression on the RHS. Regards, Malcolm