Hi, I've looked at: http://hackage.haskell.org/trac/ghc/blog/LetGeneralisationInGhc7 but still have a problem with the attached program that fails with: GHCi, version 7.1.20101010: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer-gmp ... linking ... done. Loading package base ... linking ... done. Loading package ffi-1.0 ... linking ... done. [1 of 1] Compiling Main ( HasKey.hs, interpreted ) HasKey.hs:17:10: Couldn't match type `key' with `key1' because this skolem type variable would escape: `key1' This skolem is bound by the instance declaration In the instance declaration for `Ord (Keyed x)' at the final instance for Ord. The original code comes from http://hackage.haskell.org/packages/archive/uni-util/2.2.0.0/doc/html/Util-V... Cheers Christian