随机Haskell错误.计算永远不会完成

Question

我写了一个小程序来做广义的凯撒密码.我无法弄清楚为什么我的强力解密功能无效.我所要做的就是尝试每个可能的乘数和偏移小于26的组合.另外,如果任何人都可以为"tryallcombinations"函数提出更好的方法,那将是值得赞赏的.

import Data.Char

caesarencipher::Int->Int->String->String
caesarencipher r s p = map chr $ map encipher plaintext
    where
        plaintext = map (\x->(ord x) - 97) p
        encipher p =  (mod (r*p + s) 26) + 97

caesardecipher::Int->Int->String->String
caesardecipher r s c = map chr $ map decipher ciphertext
    where
        ciphertext = map (\x->(ord x) - 97) c
        inverser x | mod (r * x) 26 == 1 = x
                   | otherwise = inverser (x + 1)
        decipher c = (mod ((inverser 1) * (c - s)) 26) + 97

tryallcombinations::String->[String]
tryallcombinations ciphertext = map (\x->x ciphertext) possibilities
    where
        rs = map caesardecipher [0..25]
        possibilities = concat $ map (\x-> map x [0..25]) rs

Answer 1

26不是素数,因此并非所有数字都具有模块化逆模26.这意味着反转有时永远不会返回,而是永远地递归.