Hello, The GHC users guide says overloading "is death to performance if left to linger in an inner loop" and one thing I noticed while playing about with the AVL lib was that using a HOF and passing the (overloaded) compare function as an explicit argument at the start seemed to give noticable a performance boost (compared with dictionary passing presumably). I'm not sure why that should be, but has anyone else noticed this? If so, maybe this advice should be added to the user guide, especially if your function repeatedly uses just one method from a class? (or maybe not if it's nonsense :-) I guess having done this there would be little to gain by using the SPECIALIZE pragma though (unless ghc also specialises HOFs). Regards -- Adrian Hey