You didn't list all functions, just input-output pairs. Each function is a map from every possible input to an output: f1 False = Nothing, f1 True = Nothing f

You didn't list all functions, just input-output pairs. Each function is a map from every possible input to an output: f1 False = Nothing, f1 True = Nothing f2 False = Nothing, f2 True = Just True ... This gives the correct 3^2 = 9 functions.