On Tue, Mar 2, 2010 at 9:06 PM, Tom Hawkins
How do I track down an reference to an undefined value? My program must not be using a library correctly because the program makes no direct use of 'undefined'. Running with +RTS -xc yields:
Test: Prelude.undefined _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
While the debugger, etc., are very useful tools, I find that often the easiest way to track down this sort of bug is to test your code function-by-function. Make sure each function does what you want it to when run in isolation; this will quickly lead to tracking down the caller of "undefined". (If your code is not structured in a way that allows this sort of testing, you might consider restructuring it to make it more modular.) Alex