úÎg81An example will explain this more than anything: , listsLongerThan3Elements :: [[a]] -> [[a]] 6 listsLongerThan3Elements = filter (length `is` (>3)) The inverse of . = listsShorterThanFourElements = filter (length `isn't` (>3)) This is " with a fixed equality condition.  Example: * data Color = White | Black deriving (Eq) 6 data ChessPiece = { color :: Color, name :: String } - whitePieces = filter (color `equals` White) predicates-0.1Data.Function.Predicateisisn'tequals