docs/_style/prism-master/examples/prism-haskell.html - master - githubmirror/CS-Notes

docs/_style/prism-master/examples/prism-haskell.html
80 строк2 KB
CyC2018
use prism-tomorrow.css
19 дек 2018, 09:09
19 дек 2018, 09:09e9e604e
<h2>Comments</h2>
<pre><code>-- Single line comment
{- Multi-line
comment -}</code></pre>

<h2>Strings and characters</h2>
<pre><code>'a'
'\n'
'\^A'
'\^]'
'\NUL'
'\23'
'\o75'
'\xFE'
"Here is a backslant \\ as well as \137, \
    \a numeric escape character, and \^X, a control character."</code></pre>

<h2>Numbers</h2>
<pre><code>42
123.456
123.456e-789
1e+3
0o74
0XAF</code></pre>

<h2>Full example</h2>
<pre><code>hGetLine h =
  wantReadableHandle_ "Data.ByteString.hGetLine" h $
    \ h_@Handle__{haByteBuffer} -> do
      flushCharReadBuffer h_
      buf <- readIORef haByteBuffer
      if isEmptyBuffer buf
         then fill h_ buf 0 []
         else haveBuf h_ buf 0 []
 where

  fill h_@Handle__{haByteBuffer,haDevice} buf len xss =
    len `seq` do
    (r,buf') <- Buffered.fillReadBuffer haDevice buf
    if r == 0
       then do writeIORef haByteBuffer buf{ bufR=0, bufL=0 }
               if len > 0
                  then mkBigPS len xss
                  else ioe_EOF
       else haveBuf h_ buf' len xss

  haveBuf h_@Handle__{haByteBuffer}
          buf@Buffer{ bufRaw=raw, bufR=w, bufL=r }
          len xss =
    do
        off <- findEOL r w raw
        let new_len = len + off - r
        xs <- mkPS raw r off

      -- if eol == True, then off is the offset of the '\n'
      -- otherwise off == w and the buffer is now empty.
        if off /= w
            then do if (w == off + 1)
                            then writeIORef haByteBuffer buf{ bufL=0, bufR=0 }
                            else writeIORef haByteBuffer buf{ bufL = off + 1 }
                    mkBigPS new_len (xs:xss)
            else do
                 fill h_ buf{ bufL=0, bufR=0 } new_len (xs:xss)

  -- find the end-of-line character, if there is one
  findEOL r w raw
        | r == w = return w
        | otherwise =  do
            c <- readWord8Buf raw r
            if c == fromIntegral (ord '\n')
                then return r -- NB. not r+1: don't include the '\n'
                else findEOL (r+1) w raw

mkPS :: RawBuffer Word8 -> Int -> Int -> IO ByteString
mkPS buf start end =
 create len $ \p ->
   withRawBuffer buf $ \pbuf -> do
   copyBytes p (pbuf `plusPtr` start) len
 where
   len = end - start</code></pre>