在haskell中将字符替换为数字

Question

我有change一些功能,可以将一些字符替换为数字.这里是:

change [] = []
change (x:xs) | x == 'A'  = '9':'9':change xs
              | x == 'B'  = '9':'8':change xs
              | otherwise = change xs

输出是:

Main> change "aAB11s"
"9998" 

但我需要这个:

Main> change "aAB11s"
"a999811s" 

我怎样才能做到这一点？

Answer 1

试试这个:

change [] = []
change (x:xs) | x == 'A'  = '9':'9':change xs
              | x == 'B'  = '9':'8':change xs
              | otherwise = x:change xs

唯一的变化就是其他方面.