strongDelete :: Eq a => a -> [a] -> [a]
strongDelete x list = let newList = Data.List.delete x list
                          in if length list == length newList
                             then error "strongDelete failed"
                             else newList
strongDelete :: Eq a => a -> [a] -> [a]
strongDelete x list = let newList = Data.List.delete x list
                          in if length list == length newList
                             then error "strongDelete failed"
                             else newList
strongDelete x list = let newList = Data.List.delete x list
                          in if length list == length newList
                             then error "strongDelete failed"
                             else newList