Hi all, I found an example program that computes grades here: http://donsbot.wordpress.com/?s=grades I copied it to my computer and tried to compile it and if failed. Strangely enough, it works on the command line using 'runhaskell'. This makes me think I didn't set up the libraries correctly. So I downloaded and re-installed the Haskell Platform from: http://hackage.haskell.org/platform/2009.2.0.2/HaskellPlatform-2009.2.0.2-se... The problem remains. I included the errors, the source and the results of runhaskell below. I hope someone can help me sort out what went wrong. Thanks, Tim C:\Documents and Settings\perry\hs>ghc -O Grades.hs Grades.o:fake:(.text+0x2f7): undefined reference to `containerszm0zi2zi0zi1_DataziMap_Tip_closure' Grades.o:fake:(.text+0x930): undefined reference to `containerszm0zi2zi0zi1_DataziMap_lvl47_closure' Grades.o:fake:(.text+0xa8b): undefined reference to `__stginit_containerszm0zi2zi0zi1_DataziMap_' Grades.o:fake:(.text+0x219): undefined reference to `containerszm0zi2zi0zi1_DataziMap_insertWithKey_info' Grades.o:fake:(.text+0x504): undefined reference to `containerszm0zi2zi0zi1_DataziMap_lookup_info' Grades.o:fake:(.text+0x90e): undefined reference to `containerszm0zi2zi0zi1_DataziMap_polyzugo1_info' Grades.o:fake:(.text+0x93f): undefined reference to `containerszm0zi2zi0zi1_DataziMap_foldr_info' Grades.o:fake:(.data+0x50): undefined reference to `containerszm0zi2zi0zi1_DataziMap_insertWithKey_closure' collect2: ld returned 1 exit status C:\Documents and Settings\perry\hs>cat Grades.hs import Data.Char import Data.Maybe import Data.List import Data.Map hiding (map) import Text.Printf main = do src <- readFile "grades.txt" let pairs = map (split.words) (lines src) grades = foldr insert empty pairs mapM_ (draw grades) (sort (keys grades)) where insert (s, g) = insertWith (++) s [g] split [name,mark] = (name, read mark) draw g s = printf "%s\t%s\tAverage: %f\n" s (show marks) avg where marks = findWithDefault (error "No such student") s g avg = sum marks / fromIntegral (length marks) :: Double C:\Documents and Settings\perry\hs>runhaskell Grades.hs Alonzo [70.0,90.0,95.0] Average: 85.0 Bob [80.0] Average: 80.0 Eugenio [69.0] Average: 69.0 Henk [79.0] Average: 79.0 Oleg [77.0] Average: 77.0 Philip [73.0] Average: 73.0 Simon [94.0,99.0,93.0] Average: 95.33333333333333 C:\Documents and Settings\perry\hs>