This code, from YAHT (Section 8.4.2, PDF pg. 119 of 192) seems to have a problem. Code below. Michael ================= [michael@localhost ~]$ ghci GHCi, version 6.10.1: http://www.haskell.org/ghc/  :? for help Loading package ghc-prim ... linking ... done. Loading package integer ... linking ... done. Loading package base ... linking ... done. Prelude> :l graph [1 of 1] Compiling Main             ( graph.hs, interpreted ) graph.hs:6:24: lexical error at character '\8217' Failed, modules loaded: none. ============== Prelude> data Graph v e = Graph [(Int,v)] [(Int,Int,e)] search :: Graph v e -> Int -> Int -> Maybe [Int] search g@(Graph vl el) src dst     | src == dst = Just [src]     | otherwise = search’ el     where search’ [] = Nothing           search’ ((u,v,_):es)               | src == u =                 case search g v dst of                   Just p -> Just (u:p)                   Nothing -> search’ es               | otherwise = search’ es