    -- | Word8 library to be used with Data.ByteString.
    -- All function assumes that 'Word8' is encoded in Latin-1 (ISO-8859-1).
    -- All utility functions are supposed to work as if
    -- those of 'Data.Char'. Exceptions are described in
    -- the function documentations.

    module Data.Word8 (
      -- * Re-exporting
        Word8
      -- * Character classification
      , isControl, isSpace, isLower, isUpper
      , isAlpha, isAlphaNum, isPrint, isDigit, isOctDigit, isHexDigit
      , isLetter, isMark, isNumber, isPunctuation, isSymbol, isSeparator
      -- * Subranges
      , isAscii, isLatin1, isAsciiUpper, isAsciiLower
      -- * Case conversion
      , toUpper, toLower, toTitle
      -- * ASCII charactors
      , _nul, _tab, _lf, _vt, _np, _cr
      , _space, _exclam, _quotedbl, _numbersign, _dollar, _percent, _ampersand, _quotesingle, _parenleft, _parenright, _asterisk, _plus, _comma, _hyphen, _period, _slash
      , _0, _1, _2, _3, _4, _5, _6, _7, _8, _9
      , _colon, _semicolon, _less, _equal, _greater, _question, _at
      , _A, _B, _C, _D, _E, _F, _G, _H, _I, _J, _K, _L, _M, _N, _O, _P, _Q, _R, _S, _T, _U, _V, _W, _X, _Y, _Z
      , _braketleft, _backslash, _bracketright, _circum, _underscore, _grave
      , _a, _b, _c, _d, _e, _f, _g, _h, _i, _j, _k, _l, _m, _n, _o, _p, _q, _r, _s, _t, _u, _v, _w, _x, _y, _z
      , _blaceleft, _bar, _braceright, _tilde, _del
      -- * Some Latin-1 charactors
      , _nbsp
      , _ordfeminine, _softhyphen, _mu, _ordmasculine
      , _s2, _s3, _s1, _1'4, _1'2, _3'4
      , _Agrave, _Odieresis, _Oslash, _Thorn
      , _germandbls, _agrave, _odieresis, _oslash, _thorn, _ydieresis
      ) where

    import Data.Word (Word8)

    ----------------------------------------------------------------

    isControl :: Word8 -> Bool
    isControl w = _nul <= w && w <= 0x1f
               || _del <= w && w <= 0x9f

    isSpace :: Word8 -> Bool
    isSpace w = w == _space
             || w == _tab
             || w == _lf
             || w == _cr
             || w == _np
             || w == _vt
             || w == _nbsp

    isLower :: Word8 -> Bool
    isLower w = isLower' w
             || w == _ordfeminine
             || w == _mu
             || w == _ordmasculine

    isLower' :: Word8 -> Bool
    isLower' w = isAsciiLower w
              || _germandbls <= w && w <= _odieresis
              || _oslash     <= w && w <= _ydieresis

    isUpper :: Word8 -> Bool
    isUpper w = isAsciiUpper w
             || _Agrave <= w && w <= _Odieresis
             || _Oslash <= w && w <= _Thorn

    isAlpha :: Word8 -> Bool
    isAlpha w = isLower w || isUpper w

    isAlphaNum :: Word8 -> Bool
    isAlphaNum w = isAlpha w || isNumber w

    isPrint :: Word8 -> Bool
    isPrint w
      | w == _softhyphen = False
    isPrint w = _space <= w && w <= _tilde
             || _nbsp  <= w && w <= _ydieresis

    isDigit :: Word8 -> Bool
    isDigit w = _0 <= w && w <= _9

    isOctDigit :: Word8 -> Bool
    isOctDigit w = _0 <= w && w <= _7

    isHexDigit :: Word8 -> Bool
    isHexDigit w = isDigit w
                || _A <= w && w <= _F
                || _a <= w && w <= _f

    isLetter :: Word8 -> Bool
    isLetter w = isLower w || isUpper w

    isMark :: Word8 -> Bool
    isMark _ = False

    isNumber :: Word8 -> Bool
    isNumber w = isDigit w
              || w == _s1
              || w == _s2
              || w == _s3
              || w == _1'4
              || w == _1'2
              || w == _3'4

    isPunctuation :: Word8 -> Bool
    isPunctuation w = w `elem` [0x21,0x22,0x23,0x25,0x26,0x27,0x28,0x29,0x2a,0x2c,0x2d,0x2e,0x2f,0x3a,0x3b,0x3f,0x40,0x5b,0x5c,0x5d,0x5f,0x7b,0x7d,0xa1,0xab,0xb7,0xbb,0xbf]

    isSymbol :: Word8 -> Bool
    isSymbol w = w `elem` [0x24,0x2b,0x3c,0x3d,0x3e,0x5e,0x60,0x7c,0x7e,0xa2,0xa3,0xa4,0xa5,0xa6,0xa7,0xa8,0xa9,0xac,0xae,0xaf,0xb0,0xb1,0xb4,0xb6,0xb8,0xd7,0xf7]

    isSeparator :: Word8 -> Bool
    isSeparator w = w == _space
                 || w == _nbsp

    ----------------------------------------------------------------

    isAscii :: Word8 -> Bool
    isAscii w = _nul <= w && w <= _del

    isLatin1 :: Word8 -> Bool
    isLatin1 _ = True

    isAsciiUpper :: Word8 -> Bool
    isAsciiUpper w = _A <= w && w <= _Z

    isAsciiLower :: Word8 -> Bool
    isAsciiLower w = _a <= w && w <= _z

    ----------------------------------------------------------------

    -- | Micro sign/mu (0xb5) and small letter Y with diaeresis (0xff) remain the same.
    toUpper :: Word8 -> Word8
    toUpper w
      | w == _germandbls = w
      | isLower' w       = w - _space
      | otherwise        = w

    toLower :: Word8 -> Word8
    toLower w
      | isUpper w = w + _space
      | otherwise = w

    -- | Micro sign/mu (0xb5) and small letter Y with diaeresis (0xff) remain the same.
    toTitle :: Word8 -> Word8
    toTitle = toUpper

    ----------------------------------------------------------------

    _nul, _tab, _lf, _vt, _np, _cr :: Word8
    _nul = 0x00
    _tab = 0x09
    _lf  = 0x0a
    _vt  = 0x0b
    _np  = 0x0c
    _cr  = 0x0d

    _space, _exclam, _quotedbl, _numbersign, _dollar, _percent, _ampersand, _quotesingle, _parenleft, _parenright, _asterisk, _plus, _comma, _hyphen, _period, _slash :: Word8
    _space       = 0x20
    _exclam      = 0x21
    _quotedbl    = 0x22
    _numbersign  = 0x23
    _dollar      = 0x24
    _percent     = 0x25
    _ampersand   = 0x26
    _quotesingle = 0x27
    _parenleft   = 0x28
    _parenright  = 0x29
    _asterisk    = 0x2a
    _plus        = 0x2b
    _comma       = 0x2c
    _hyphen      = 0x2d
    _period      = 0x2e
    _slash       = 0x2f

    _0, _1, _2, _3, _4, _5, _6, _7, _8, _9 :: Word8
    _0 = 0x30
    _1 = 0x31
    _2 = 0x32
    _3 = 0x33
    _4 = 0x34
    _5 = 0x35
    _6 = 0x36
    _7 = 0x37
    _8 = 0x38
    _9 = 0x39

    _colon, _semicolon, _less, _equal, _greater, _question, _at :: Word8
    _colon      = 0x3a
    _semicolon  = 0x3b
    _less       = 0x3c
    _equal      = 0x3d
    _greater    = 0x3e
    _question   = 0x3f
    _at         = 0x40

    _A, _B, _C, _D, _E, _F, _G, _H, _I, _J, _K, _L, _M, _N, _O, _P, _Q, _R, _S, _T, _U, _V, _W, _X, _Y, _Z :: Word8
    _A = 0x41
    _B = 0x42
    _C = 0x43
    _D = 0x44
    _E = 0x45
    _F = 0x46
    _G = 0x47
    _H = 0x48
    _I = 0x49
    _J = 0x4a
    _K = 0x4b
    _L = 0x4c
    _M = 0x4d
    _N = 0x4e
    _O = 0x4f
    _P = 0x50
    _Q = 0x51
    _R = 0x52
    _S = 0x53
    _T = 0x54
    _U = 0x55
    _V = 0x56
    _W = 0x57
    _X = 0x58
    _Y = 0x59
    _Z = 0x5a

    _braketleft, _backslash, _bracketright, _circum, _underscore, _grave :: Word8
    _braketleft   = 0x5b
    _backslash    = 0x5c
    _bracketright = 0x5d
    _circum       = 0x5e
    _underscore   = 0x5f
    _grave        = 0x60

    _a, _b, _c, _d, _e, _f, _g, _h, _i, _j, _k, _l, _m, _n, _o, _p, _q, _r, _s, _t, _u, _v, _w, _x, _y, _z :: Word8
    _a = 0x61
    _b = 0x62
    _c = 0x63
    _d = 0x64
    _e = 0x65
    _f = 0x66
    _g = 0x67
    _h = 0x68
    _i = 0x69
    _j = 0x6a
    _k = 0x6b
    _l = 0x6c
    _m = 0x6d
    _n = 0x6e
    _o = 0x6f
    _p = 0x70
    _q = 0x71
    _r = 0x72
    _s = 0x73
    _t = 0x74
    _u = 0x75
    _v = 0x76
    _w = 0x77
    _x = 0x78
    _y = 0x79
    _z = 0x7a

    _blaceleft, _bar, _braceright, _tilde, _del :: Word8
    _blaceleft  = 0x7b
    _bar        = 0x7c
    _braceright = 0x7d
    _tilde      = 0x7e
    _del        = 0x7f

    _nbsp :: Word8
    _nbsp = 0xa0

    _ordfeminine, _softhyphen, _mu, _ordmasculine :: Word8
    _ordfeminine  = 0xaa
    _softhyphen   = 0xad
    _mu           = 0xb5
    _ordmasculine = 0xba

    _s2, _s3, _s1, _1'4, _1'2, _3'4  :: Word8
    _s2 = 0xb2
    _s3 = 0xb3
    _s1 = 0xb9
    _1'4 = 0xbc
    _1'2 = 0xbd
    _3'4 = 0xbe

    _Agrave, _Odieresis, _Oslash, _Thorn :: Word8
    _Agrave    = 0xc0
    _Odieresis = 0xd6
    _Oslash    = 0xd8
    _Thorn     = 0xde

    _germandbls, _agrave, _odieresis, _oslash, _thorn, _ydieresis :: Word8
    _germandbls = 0xdf
    _agrave     = 0xe0
    _odieresis  = 0xf6
    _oslash     = 0xf8
    _thorn      = 0xfe
    _ydieresis  = 0xff