问题描述
限时送ChatGPT账号..Haskell 中的 show 函数似乎没有做它应该做的:
The show function in Haskell doesn't seem to do what it should:
Prelude> let str = "stack\n\noverflow"
Prelude> putStrLn str
stack
overflow
Prelude> show str
"\"Stack\\n\\n\\noverflow\""
Prelude>
当我声明函数时,我通常将类型签名设为Show,这不会正确处理换行符.我希望它将 \n
视为换行符,而不是字面上的 "\n"
.当我将类型更改为 String 时,函数工作正常.但我必须为整数、浮点数等实现一个单独的函数.
When I declare functions, I normally put the type signatures as Show, which doesn't deal with newlines correctly. I want it to treat \n
as newlines, not literally "\n"
. When I change the type to String, the functions work fine. But I'd have to implement a seperate function for integers, floats, etc, etc.
例如,我可以声明一个函数:
For example, I may declare a function:
foo :: (Show x) => x -> IO ()
foo x = do
putStrLn $ show x
...并这样称呼它:
foo "stack\n\noverflow"
foo 6
foo [1..]
我如何让函数返回预期的内容?IE.哪个函数类似于 show
但可以返回包含换行符的字符串?
How would I get the function to return what's expected? I.e. which function is similar to show
but can return strings containing newlines?
推荐答案
Haskell 中 show 方法的契约是它产生一个字符串,当评估时,产生显示的值.
The contract of the show method in Haskell is that it produce a string that, when evaluated, yields the value that was shown.
Prelude> let str = "stack\n\noverflow"
Prelude> putStrLn str
stack
overflow
Prelude> putStrLn (show str)
"stack\n\noverflow"
Prelude>
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