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在 Python 中,我可以locale.format根据语言环境设置漂亮地打印数字:

>>> import locale
>>> locale.setlocale(locale.LC_ALL, "en_US.UTF-8")
'en_US.UTF-8'
>>> locale.format("%.2f",1234567.89,grouping=True)
'1,234,567.89'

我怎样才能在 Haskell 中做同样的事情?我看到有localeconv 和 setlocale绑定,但是是否有一个通用的漂亮打印机尊重Lconv

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1 回答 1

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我会说,如果缺少相关库,那么您可以自己编写一个(显而易见的选择,并不容易),或者为所需的函数编写一个绑定。例如,只sprintf允许 sprintf 的受限绑定加倍:

双.hs:

{-# INCLUDE "double.h" #-}
{-# LANGUAGE ForeignFunctionInterface #-}
module Double (cPrintf) where

import Foreign
import Foreign.C.Types
import System.IO.Unsafe
import qualified Data.ByteString as B

foreign import ccall "double.h toString"
 c_toString :: CDouble -> (Ptr Word8) -> CInt -> IO CInt

buf = unsafePerformIO $ mallocBytes 64

cPrintf :: Double -> B.ByteString
cPrintf n = B.pack $ unsafePerformIO $ do
   len <- c_toString (realToFrac n) buf 64
   peekArray (fromIntegral len) buf

双.h:

int toString(double a, char *buffer, int bufferLen);

双.c:

#include <stdio.h>
#include "double.h"

int toString(double a, char *buffer, int bufferLen) {
 return snprintf(buffer, bufferLen, "%f", a);
}

构建为:

gcc -c double.c
ghc --make Main.hs double.o
于 2009-11-12T19:26:12.493 回答