Haskell：将 Int 转换为 String

Question

I know you can convert a String to an number with read :我知道您可以使用read将String转换为数字：

Prelude> read "3" :: Int
3
Prelude> read "3" :: Double 
3.0

But how do you grab the String representation of an Int value?但是如何获取Int值的String表示呢？

Answer 1

The opposite of read is show . read的反面是show 。

Prelude> show 3
"3"

Prelude> read $ show 3 :: Int
3

Answer 2

Anyone who is just starting with Haskell and trying to print an Int, use:任何刚开始使用 Haskell 并尝试打印 Int 的人，请使用：

module Lib
    ( someFunc
    ) where

someFunc :: IO ()
x = 123
someFunc = putStrLn (show x)

Answer 3

An example based on Chuck's answer:一个基于查克回答的例子：

myIntToStr :: Int -> String
myIntToStr x
    | x < 3     = show x ++ " is less than three"
    | otherwise = "normal"

Note that without the show the third line will not compile.请注意，如果没有show ，第三行将无法编译。

Answer 4

You can use show:您可以使用显示：

show 3

What I want to add is that the type signature of show is the following:我想补充的是，show 的类型签名如下：

show :: a -> String

And can turn lots of values into string not only type Int .并且可以将大量值转换为字符串，而不仅仅是类型Int 。

For example:例如：

show [1,2,3]

Here is a reference:这是一个参考：