allJust :: [Maybe a] -> Maybe [a]
allJust l = if all isJust l then Just $! map fromJust l
            else Nothing
allJust :: [Maybe a] -> Maybe [a]
allJust l = if all isJust l then Just $! map fromJust l
            else Nothing
allJust l = if all isJust l then Just $! map fromJust l
            else Nothing