Haskell 从Get monad读取位的一元方法

我需要从Get monad中读取一些位。现在我的代码看起来像

readBits :: Int -> Int -> Get (Word32, Int)
readBits count state = ...

readValue :: Get (Word32, Word32)
readValue = do
   -- read fst bit count 
   (bits1, s0) <- readBits 5 0
   -- read bits1 bits as fst
   (fst, s1) <- readBits bits1 s0
   -- read snd bit count
   (bits2, s2) <- readBits 5 s1
   -- read bits2 bits as snd
   (snd, s3) <- readBits bits2 s2  
   -- flush incomplete byte
   when (s3 /= 0) $ skip 1
   return (fst, snd)

readBits:：Int->Int->Get（Word32，Int）
读取位计数状态=。。。
readValue:：Get（Word32，Word32）
readValue=do
--读取fst位计数
（bits1，s0）这是Monad变压器最典型的用例

您已经正确定义了大部分结构。回答你的问题

What functions should I implement? 


首先需要将
Get
monad包装到
StateT
转换器中，以获取
位读取器

您需要使用
get
为
readBits
实现正确的定义，以获取当前状态，并使用
put
将状态保存回来
您需要运行用
位读取器
包装的代码，以在
get
Monad中获取输出。因此，您需要使用
runStateT
定义
runBitReader

来回答你的下一个问题

How should they be implemented?

我已经给出了可能的实施方案。您仍然需要定义一些函数才能使其正常工作

import Control.Monad.State 
import qualified Control.Monad.State as ST
import Data.Binary 

type BitReader = StateT Int Get

readBits' :: Int -> Int -> Get (Word32, Int)
readBits' = undefined   

readBits :: Int -> BitReader Word32
readBits n = do 
    s0 <- ST.get 
    (a,s1) <- lift $ readBits' n s0
    ST.put s1 
    return a


runBitReader :: BitReader a -> Get a
runBitReader w = do 
    (a,s) <- runStateT w 0
    return a

readValue = do
      fst <- readBits 5
      snd <- readBits 10
      return (fst, snd) 

import Control.Monad.State
导入合格的控件。单子状态为ST
导入数据。二进制
类型BitReader=StateT Int Get
readBits'：：Int->Int->Get（Word32，Int）
readBits'=未定义
readBits:：Int->BitReader Word32
读取位n=do
s0
import Control.Monad.State 
import qualified Control.Monad.State as ST
import Data.Binary 

type BitReader = StateT Int Get

readBits' :: Int -> Int -> Get (Word32, Int)
readBits' = undefined   

readBits :: Int -> BitReader Word32
readBits n = do 
    s0 <- ST.get 
    (a,s1) <- lift $ readBits' n s0
    ST.put s1 
    return a


runBitReader :: BitReader a -> Get a
runBitReader w = do 
    (a,s) <- runStateT w 0
    return a

readValue = do
      fst <- readBits 5
      snd <- readBits 10
      return (fst, snd)