Hi, In Prelude.hs you can find the definition enumFrom x = map toEnum [ fromEnum x ..] Load a file.hs of just one line: data TBool = Falsity | Undefined |Truth deriving (Enum, Show) Then, I evaluate enumFrom Falsity and, as expected, it gives [Falsity,Undefined,Truth] However, the expression map toEnum [ fromEnum Falsity ..] gives first an ambiguity problem and then the problem I expected Main> map toEnum [ fromEnum Falsity ..] ERROR - Unresolved overloading *** Type : Enum a => [a] *** Expression : map toEnum (enumFrom (fromEnum Falsity)) Main> map toEnum [ fromEnum Falsity ..]::[TBool] [Falsity,Undefined,Truth, Program error: {_toEnum TBool_Falsity 3} (98 reductions, 301 cells) Why the function enumFrom works perfectly in spite of its erroneous definition? Thanks in advance, Paqui P.D. I am using the || || || || || || ||__ Hugs 98: Based on the Haskell 98 standard ||___|| ||__|| ||__|| __|| Copyright (c) 1994-2002 ||---|| ___|| World Wide Web: http://haskell.org/hugs || || Report bugs to: hugs-bugs@haskell.org || || Version: Nov 2002 --------------------------------- Paqui Lucio Dpto de LSI Facultad de Informática Paseo Manuel de Lardizabal, 1 20080-San Sebastián SPAIN --------------------------------- e-mail: paqui.lucio@ehu.es Tfn: (+34) (9)43 015049 Fax: (+34) (9)43 015590 Web: http://www.sc.ehu.es/paqui ---------------------------------