bytestring和string

如何解决以下问题：

import Data.ByteString.Lazy as BS  (readFile, ByteString, unpack, fromStrict)
import Data.ByteString.Char8 as C8 (pack)
import Data.ByteString.UTF8        (toString)
import Data.Char                   (chr)

stringToBS :: String -> BS.ByteString
stringToBS str = BS.fromStrict $ C8.pack str

recode :: String -> String
recode str = toString $ urlDecode True (stringToBS str)

注意我需要让他们知道我已经设置的类型

编译时出错：

Couldn't match expected type ‘Data.ByteString.Internal.ByteString’
            with actual type ‘ByteString’
NB: ‘Data.ByteString.Internal.ByteString’
      is defined in ‘Data.ByteString.Internal’
    ‘ByteString’ is defined in ‘Data.ByteString.Lazy.Internal’
In the second argument of ‘urlDecode’, namely ‘(stringToBS str)’
In the second argument of ‘($)’, namely
  ‘urlDecode True (stringToBS str)’

---

我怎样才能解决这个错误呢？

我在Hackage中找不到适合您使用的

urlDecode

，所以我不能确定，但它可能需要严格的

ByteString

，而不是懒惰的，在这种情况下，下面的方法应该有效

import Data.ByteString as BS  (readFile, ByteString, unpack)
import Data.ByteString.Char8 as C8 (pack)
import Data.ByteString.UTF8        (toString)
import Data.Char                   (chr)

recode :: String -> String
recode str = toString $ urlDecode True (C8.pack str)

---

不要将

ByteString

的惰性变体用于

urlDecode

。什么是

urlDecode

（键入！）？您从哪里获得

urlDecode

？