To the Hugs-Bugs problemsolvers, The following lines give a fatal error trying to match with convect [1] in Winhugs running under windows 98: convect [] = [] convect (h:t) = convect([h]) ++ convect(t) convect a = a There is no error message of Hugs itself. The fatal error message comes from windows Hugs is exited by Windows. Greetings, Sander van Tuijl.