有没有办法在Haskell中使用printf格式的打印？ [英] Is there a way to use print with the formats of printf in Haskell?

问题描述

为了获得Haskell的进一步经验，我开始使用print和printf。

我想尝试打印一个数组（好几个，但这只是一个开始），我想用格式％+ .4f，这意味着我会得到：

  +2.1234或-1.2345 
  

然而，我注意到使用printf打印数组非常困难，所以我尝试切换到打印。以这种方式打印列表似乎更容易，但我不确定如何使用与printf相同的格式打印列表元素。

我的清单看起来像这样：

  [ -  1.2,2.3,4.7，-6.850399] 
   
 
 
 > 
 
 
  putStrLn $ concatMap（printf％+。4f\\\
）[-1.2,2.3,4.7，-6.850399] 
 mapM_（printf％+。4f \ n）[-1.2,2.3,4.7，-6.850399] 
  
编辑：为了遍历两个列表： 
 
 
  putStrLn $（concatMap。concatMap）（printf％+。4f \ n）[[-1.2,2.3]，[4.7，-6.850399]] 
（mapM_。mapM_）（printf％+。4f\\\
）[[-1.2,2.3]，[ 4.7，-6.850399]] 
  
 
On my quest to acquire further experience in Haskell, I started working with print and printf. 


I wanted to try to print an array (well, several, but it's just a start) and I wanted to use the format "%+.4f", meaning I would get:
+2.1234 or -1.2345
I noticed however that it's pretty hard to print an array using printf, so I tried switching to print. It seems easier to print a list this way, but I'm not sure how I can print the elements of the list using the same format I used for printf.

My list looks something like this:
[-1.2, 2.3, 4.7, -6.850399]

解决方案
Two variants that should do the same, using the two possible return types of printf:
putStrLn $ concatMap (printf "%+.4f\n") [-1.2, 2.3, 4.7, -6.850399]
mapM_ (printf "%+.4f\n") [-1.2, 2.3, 4.7, -6.850399]
Edit: For traversing two lists deep:
putStrLn $ (concatMap . concatMap) (printf "%+.4f\n") [[-1.2, 2.3], [4.7, -6.850399]]
(mapM_ . mapM_) (printf "%+.4f\n") [[-1.2, 2.3], [4.7, -6.850399]]


                        
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