相关疑难解决方法(0)

这是一种解决欧拉问题43的方法(如果没有给出正确答案,请告诉我).是否有monad或其他合成糖可以帮助跟踪notElem条件？

toNum xs = foldl (\s d -> s*10+d) 0 xs

numTest xs m = (toNum xs) `mod` m == 0

pandigitals = [ [d0,d1,d2,d3,d4,d5,d6,d7,d8,d9] |
                d7 <- [0..9],
                d8 <- [0..9], d8 `notElem` [d7],
                d9 <- [0..9], d9 `notElem` [d8,d7],
                numTest [d7,d8,d9] 17,
                d5 <- [0,5],  d5 `notElem` [d9,d8,d7],
                d3 <- [0,2,4,6,8], d3 `notElem` [d5,d9,d8,d7],
                d6 <- [0..9], d6 `notElem` [d3,d5,d9,d8,d7],
                numTest [d6,d7,d8] 13,
                numTest [d5,d6,d7] 11,
                d4 <- [0..9], d4 `notElem` [d6,d3,d5,d9,d8,d7],
                numTest [d4,d5,d6] 7,
                d2 …