第39回　一般向けの「Haskell Platform」とインストール・ツールの「cabalコマンド」

Prelude Foreign.C.Types> :i CWchar
newtype CWchar = Foreign.C.Types.CWchar GHC.Int.Int32
        -- Defined in Foreign.C.Types
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instance Show CWchar -- Defined in Foreign.C.Types

Prelude Foreign.C.Types> :i CWchar
newtype CWchar = Foreign.C.Types.CWchar GHC.Word.Word16
        -- Defined in Foreign.C.Types
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instance Show CWchar -- Defined in Foreign.C.Types
Prelude Foreign.C.Types> :m Foreign.C.String
Prelude Foreign.C.String> :browse
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type CWString = GHC.Ptr.Ptr Foreign.C.Types.CWchar
type CWStringLen = (GHC.Ptr.Ptr Foreign.C.Types.CWchar, Int)
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newCWString :: String -> IO CWString
newCWStringLen :: String -> IO CWStringLen
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peekCWString :: CWString -> IO String
peekCWStringLen :: CWStringLen -> IO String
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withCWString :: String -> (CWString -> IO a) -> IO a
withCWStringLen :: String -> (CWStringLen -> IO a) -> IO a

Prelude System.IO> putStrLn "テスト"
テスト

{-# NOINLINE localeEncoding #-}
localeEncoding :: TextEncoding
localeEncoding = unsafePerformIO $ fmap codePageEncoding getCurrentCodePage

codePageEncoding :: Word32 -> TextEncoding
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codePageEncoding cp = maybe latin1 buildEncoding (lookup cp codePageMap)

Prelude System.IO> :t hSetEncoding
hSetEncoding :: Handle -> TextEncoding -> IO ()
Prelude System.IO> :browse
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latin1 :: TextEncoding
localeEncoding :: TextEncoding
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utf16 :: TextEncoding
utf16be :: TextEncoding
utf16le :: TextEncoding
utf32 :: TextEncoding
utf32be :: TextEncoding
utf32le :: TextEncoding
utf8 :: TextEncoding
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Prelude System.IO> :t hGetEncoding
hGetEncoding :: Handle -> IO (Maybe TextEncoding)

Prelude System.IO> :t stdin
stdin :: Handle
Prelude System.IO> :t stdout
stdout :: Handle
Prelude System.IO> :t stderr
stderr :: Handle

module Unicode where
import System.IO

main = do
    h <- openFile "test.txt" WriteMode
    hSetEncoding h utf8
    hPutStrLn h "テスト"
    hClose h

テスト

Prelude System.IO> hSetEncoding stdout utf8
Prelude System.IO> hPutStrLn stdout "テスト"
繝・せ繝
Prelude System.IO> putStrLn "テスト"
繝・せ繝

-- | Write a string to the standard output device
-- (same as 'hPutStr' 'stdout').
putStr          :: String -> IO ()
putStr s        =  hPutStr stdout s
-- | The same as 'putStr', but adds a newline character.
putStrLn        :: String -> IO ()
putStrLn s      =  do putStr s
                      putChar '\n'

Prelude System.IO> print "テスト"
"\12486\12473\12488"

instance  Show Char  where
    showsPrec _ '\'' = showString "'\\''"
    showsPrec _ c    = showChar '\'' . showLitChar c . showChar '\''
    showList cs = showChar '"' . showl cs
                 where showl ""       s = showChar '"' s
                       showl ('"':xs) s = showString "\\\"" (showl xs s)
                       showl (x:xs)   s = showLitChar x (showl xs s)
                -- Making 's' an explicit parameter makes it clear to GHC
                -- that showl has arity 2, which avoids it allocating an extra lambda
                -- The sticking point is the recursive call to (showl xs), which
                -- it can't figure out would be ok with arity 2.

-- | Convert a character to a string using only printable characters,
-- using Haskell source-language escape conventions.  For example:
--
-- > showLitChar '\n' s  =  "\\n" ++ s
--
showLitChar                :: Char -> ShowS
showLitChar c s | c > '\DEL' =  showChar '\\' (protectEsc isDec (shows (ord c)) s)
showLitChar '\DEL'         s =  showString "\\DEL" s
showLitChar '\\'           s =  showString "\\\\" s
showLitChar c s | c >= ' '   =  showChar c s
showLitChar '\a'           s =  showString "\\a" s
showLitChar '\b'           s =  showString "\\b" s
showLitChar '\f'           s =  showString "\\f" s
showLitChar '\n'           s =  showString "\\n" s
showLitChar '\r'           s =  showString "\\r" s
showLitChar '\t'           s =  showString "\\t" s
showLitChar '\v'           s =  showString "\\v" s
showLitChar '\SO'          s =  protectEsc (== 'H') (showString "\\SO") s
showLitChar c              s =  showString ('\\' : asciiTab!!ord c) s
        -- I've done manual eta-expansion here, becuase otherwise it's
        -- impossible to stop (asciiTab!!ord) getting floated out as an MFE

Prelude> :i Read
class Read a where
  readsPrec :: Int -> ReadS a
  readList :: ReadS [a]
  GHC.Read.readPrec :: Text.ParserCombinators.ReadPrec.ReadPrec a
  GHC.Read.readListPrec ::
    Text.ParserCombinators.ReadPrec.ReadPrec [a]
        -- Defined in GHC.Read
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instance (Read a) => Read [a] -- Defined in GHC.Read
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instance Read Char -- Defined in GHC.Read
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module Unicode where
import System.IO

main = do
    h <- openFile "test.txt" WriteMode
    hSetEncoding h utf8
    hPutStrLn h (read (show "テスト")::String)
    hClose h

テスト