如何将数字列表转换为 Haskell 中的字符串列表

Question

如何在 Haskell 中将数字列表转换为字符串列表（一个字符串 = 列表中的一个数字）。

[整数] -> [字符串]

示例：[1,2,3,4] -> ["1","2","3","4"]

Answer 1

如果您有函数 f :: a -> b，则 map f :: [a] -> [b] 对所有列表元素应用 f。

函数 show 可以转换 "printable" 类型的字符串表示形式。特别是，show 的一种可能类型是 Int -> String.

同时使用这两种工具。

Answer 2

使用列表 monad:

f :: [Int] -> String
f xs = do 
         x <- xs
         return $ show x

或等同于：

f' :: [Int] -> [String]
f' = (>>= return.show)

Answer 3

如果您需要编写一个函数来打印从 0 开始的元素，这可能是另一种解决方案

cp_log :: (Show a) => [a] -> String

cp_log [] = ""
cp_log [x] = (show x)
cp_log (x:xs) = (show x) ++ ", " ++ cp_log xs

一个完整的例子可以是下面这个

cp_log :: (Show a) => [a] -> String
    
cp_log [] = ""
cp_log [x] = (show x)
cp_log (x:xs) = (show x) ++ ", " ++ cp_log xs

quick_sort :: (Ord a) => [a] -> [a]
quick_sort [] = []
quick_sort (x:xs) =
  let smaller = quick_sort [a | a <- xs, a <= x]
      bigger = quick_sort [a | a <- xs, a > x]
  in smaller ++ [x] ++ bigger

main =
  let sorted = (quick_sort [4, 5, 3, 2, 4, 3, 2])
  in putStrLn (cp_log sorted)

如何将数字列表转换为 Haskell 中的字符串列表

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