Print和putStrLn在Haskell中的区别 [英] Difference between Print and putStrLn in Haskell

问题描述

我很困惑。我尝试使用 print ，但我知道有人应用 putStrLn 。

  print $ function 
 putStrLn $ function 
  putStrLn 函数需要一个<$ c $ <$ pre $ b $  String 并将其显示在屏幕上，后面跟着一个换行符（ put   str ，后跟一个新的 L  i  n  e）。
 
 
因为它只适用于字符串 s，一个常见的习惯用法是将任何对象转换为 String ，然后将 putStrLn 应用于显示它。将对象转换为 String 的通用方法是使用 show 函数，因此您的代码最终会以很多
  putStrLn（显示1）
 putStrLn（显示[1,2,3]）
 putStrLn（show（Just 42））
  
一旦您注意到了，定义并不是很大一个将字符串转换为一个字符串的函数
  print x = putStrLn（show x）
  
这正是 print 函数是。
 
I am confused. I try to use print, but I know people apply putStrLn. What are the real differences between them?
 print $ function 
 putStrLn $ function

解决方案
The function putStrLn takes a String and displays it to the screen, followed by a newline character (put a String followed by a new Line).

Because it only works with Strings, a common idiom is to take any object, convert it to a String, and then apply putStrLn to display it. The generic way to convert an object to a String is with the show function, so your code would end up with a lot of
putStrLn (show 1)
putStrLn (show [1, 2, 3])
putStrLn (show (Just 42))
Once you notice that, it's not a very big stretch to define a function that converts to a String and displays the string in one step
print x = putStrLn (show x)
which is exactly what the print function is.

                        
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