[Haskell-cafe] Pathological overloaded function

Could anyone chip in with examples of a pathological overloaded functions in relation to the GHC Guide 6.2:

Overloaded functions are not your friend: Haskell's overloading (using type classes) is elegant, neat, etc., etc., but it is death to performance if left to linger in an inner loop. How can you squash it?

Give explicit type signatures: Signatures are the basic trick; putting them on exported, top-level functions is good software-engineering practice, anyway. (Tip: using -fwarn-missing-signatures can help enforce good signature-practice).

http://lambda.haskell.org/platform/doc/current/ghc-doc/users_guide/faster.ht... Best Regards, Simon