Haskell printf转换为字符串 [英] Haskell printf to string

问题描述

Haskell中是否有sprintf等效项?

Is there a sprintf equivalent in Haskell?

我需要将双精度值转换为字符串并将其格式化为字符串.

I need to convert and format double values into strings.

还有没有使用 printf 类功能的另一种方法吗?

Is there another way without using printf kind of functions?

主要问题是避免:

Prelude> putStrLn myDoubleVal
1.7944444444444447e-2

相反，我想要这个:

Prelude> putStrLn . sprintf "%.2f" $ myDoubleVal
1.79

推荐答案

是的，它位于

Yes, it's in the Text.Printf module, and it's just called printf.

> import Text.Printf
> let x = 1.14907259
> putStrLn . printf "%.2f" $ x
1.15

请注意，printf的返回类型已重载，因此它可以返回String(如上例所示)，但也可以返回执行打印的I/O操作，因此您实际上不需要调用putStrLn:

Note that the return type of printf is overloaded, so that it's capable of returning a String (as in the example above) but it's also capable of returning an I/O action that does the printing, so you don't actually need the call to putStrLn:

> printf "%.2f\n" x
1.15

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