Hi. I have the next definitions: type Ocurrence = (String, Int) type Inside = [Ocurrence] data Pattern = Return Inside | Abort | Filter (Ocurrence -> Bool) Pattern beyond :: Pattern -> Pattern beyond (Filter pred Abort) = Abort -- more definitions of beyond optimous :: Pattern -> Pattern optimous p = fixPoint beyond p where fixPoint f x = if(f x == x) then x else fixPoint f (f x) When I load the program an error is produced: ERROR - An instance of Eq (Event -> Bool) is required to derive Eq Pattern I put: data Pattern = Return Inside | Abort | Filter (Ocurrence -> Bool) Pattern deriving (Eq) and a new error was produced: ERROR - An instance of Eq (Ocurrence -> Bool) is required to derive Eq Pattern Who can I do an instance of Eq (Ocurrence -> Bool)? Is there another option to avoid the error? Regards Ulises _________________________________________________________________ Express yourself instantly with MSN Messenger! Download today it's FREE! http://messenger.msn.click-url.com/go/onm00200471ave/direct/01/