haskell - Haskell 中的新行

Question

我一直在浏览以前提出的问题，但找不到解决我的问题的答案，尽管我认为至少其中一个可以解决。我只是想在函数内部的字符串之间添加换行符。每当我向字符串添加“\n”时，它只会打印“\n”

import Data.List
-- aRow takes number of columns as argument
-- The idea is to use this function with the number of columns as argument.
-- Example, if we want 3 columns, we'd say aRow 3, and get "+---+---+---+"

aRow :: Int -> String
aRow n = "+" ++ take (4*n) (intercalate "" (repeat "---+")) ++ "\n|" ++ take (4*n) (intercalate "" (repeat "   |"))

这是我得到的输出

"+---+---+---+---+\n|   |   |   |   |"

我更喜欢

"+---+---+---+---+" 
"|   |   |   |   |"

各行位于不同的行上(竖线之间应该有 3 个空格，请忽略我的格式。我主要是想让换行符正常工作)。谢谢。

Answer 1

https://stackoverflow.com/a/5944062/1848654 :

If you just evaluate a string expression in ghci without using putStr or putStrLn, it will just call show on it, so for example the string "foo\n" will display as "foo\n" in ghci, but that does not change the fact that it's a string containing a newline and it will print that way, once you output it using putStr.

长话短说，您可能需要使用 putStr，因为 Haskell 默认在该字符串上使用 show 并显示 \n > 很明显，就像它在这里为您所做的那样。

示例:

import Data.List

main = putStrLn(aRow 4) 

aRow :: Int -> String
aRow n = "+" ++ take (4*n) (intercalate "" (repeat "---+")) ++ "\n|" ++      take (4*n) (intercalate "" (repeat "   |"))