Dear Tomi, all, I agree with everyone on this list that there is a good reason for being picky about numeric types. However, when you're simply trying to understand a small problem or puzzle, the rather intricate numeric part of the type system can be prohibitively complex. I'm no Haskell guru, but I don't consider myself a novice anymore. Still, I tend to waste time on numeric stuff when trying to understand a simple and small problem. To avoid this, I wrote a Number module that provides a type Number that is of all of the standard numeric type classes. Especially for toy problems - I keep repeating this, because my Number module is NOT FIT for production code - it is the lazy man's solution to all the fuss about numbers. I'm lazy, me like. You can have a look at the Number module here: http://www.cs.utwente.nl/~holzensp/Number.hs Now, whenever I've hacked together a small program, it nearly always works. When it doesn't, it generally complains about some numeric value somewhere. I just stick a "toNumber" in front, et voilà! :D Regards, Philip PS. I know, people will want to kill me for putting all numbers back together in a sluggish single type, but in my defense: aren't we all a tiny bit lazy every once in a while?