    {-# LANGUAGE Trustworthy #-}
    {-# LANGUAGE CPP, NoImplicitPrelude #-}
    {-# OPTIONS_HADDOCK hide #-}

    -----------------------------------------------------------------------------
    -- |
    -- Module      :  GHC.Unicode
    -- Copyright   :  (c) The University of Glasgow, 2003
    -- License     :  see libraries/base/LICENSE
    --
    -- Maintainer  :  cvs-ghc@haskell.org
    -- Stability   :  internal
    -- Portability :  non-portable (GHC extensions)
    --
    -- Implementations for the character predicates (isLower, isUpper, etc.)
    -- and the conversions (toUpper, toLower).  The implementation uses
    -- libunicode on Unix systems if that is available.
    --
    -----------------------------------------------------------------------------

    module GHC.Unicode (
            isAscii, isLatin1, isControl,
            isAsciiUpper, isAsciiLower,
            isPrint, isSpace,  isUpper,
            isLower, isAlpha,  isDigit,
            isOctDigit, isHexDigit, isAlphaNum,
            toUpper, toLower, toTitle,
            wgencat
        ) where

    import GHC.Base
    import GHC.Char        (chr)
    import GHC.Real
    import GHC.Num

    #include "HsBaseConfig.h"

    -- | Selects the first 128 characters of the Unicode character set,
    -- corresponding to the ASCII character set.
    isAscii                 :: Char -> Bool
    isAscii c               =  c <  '\x80'

    -- | Selects the first 256 characters of the Unicode character set,
    -- corresponding to the ISO 8859-1 (Latin-1) character set.
    isLatin1                :: Char -> Bool
    isLatin1 c              =  c <= '\xff'

    -- | Selects ASCII lower-case letters,
    -- i.e. characters satisfying both 'isAscii' and 'isLower'.
    isAsciiLower :: Char -> Bool
    isAsciiLower c          =  c >= 'a' && c <= 'z'

    -- | Selects ASCII upper-case letters,
    -- i.e. characters satisfying both 'isAscii' and 'isUpper'.
    isAsciiUpper :: Char -> Bool
    isAsciiUpper c          =  c >= 'A' && c <= 'Z'

    -- | Selects control characters, which are the non-printing characters of
    -- the Latin-1 subset of Unicode.
    isControl               :: Char -> Bool

    -- | Selects printable Unicode characters
    -- (letters, numbers, marks, punctuation, symbols and spaces).
    isPrint                 :: Char -> Bool

    -- | Returns 'True' for any Unicode space character, and the control
    -- characters @\\t@, @\\n@, @\\r@, @\\f@, @\\v@.
    isSpace                 :: Char -> Bool
    -- isSpace includes non-breaking space
    -- The magic 0x377 isn't really that magical. As of 2014, all the codepoints
    -- at or below 0x377 have been assigned, so we shouldn't have to worry about
    -- any new spaces appearing below there. It would probably be best to
    -- use branchless ||, but currently the eqLit transformation will undo that,
    -- so we'll do it like this until there's a way around that.
    isSpace c
      | uc <= 0x377 = uc == 32 || uc - 0x9 <= 4 || uc == 0xa0
      | otherwise = iswspace (ord c) /= 0
      where
        uc = fromIntegral (ord c) :: Word

    -- | Selects upper-case or title-case alphabetic Unicode characters (letters).
    -- Title case is used by a small number of letter ligatures like the
    -- single-character form of /Lj/.
    isUpper                 :: Char -> Bool

    -- | Selects lower-case alphabetic Unicode characters (letters).
    isLower                 :: Char -> Bool

    -- | Selects alphabetic Unicode characters (lower-case, upper-case and
    -- title-case letters, plus letters of caseless scripts and modifiers letters).
    -- This function is equivalent to 'Data.Char.isLetter'.
    isAlpha                 :: Char -> Bool

    -- | Selects alphabetic or numeric digit Unicode characters.
    --
    -- Note that numeric digits outside the ASCII range are selected by this
    -- function but not by 'isDigit'.  Such digits may be part of identifiers
    -- but are not used by the printer and reader to represent numbers.
    isAlphaNum              :: Char -> Bool

    -- | Selects ASCII digits, i.e. @\'0\'@..@\'9\'@.
    isDigit                 :: Char -> Bool
    isDigit c               =  (fromIntegral (ord c - ord '0') :: Word) <= 9

    -- We use an addition and an unsigned comparison instead of two signed
    -- comparisons because it's usually faster and puts less strain on branch
    -- prediction. It likely also enables some CSE when combined with functions
    -- that follow up with an actual conversion.

    -- | Selects ASCII octal digits, i.e. @\'0\'@..@\'7\'@.
    isOctDigit              :: Char -> Bool
    isOctDigit c            =  (fromIntegral (ord c - ord '0') :: Word) <= 7

    -- | Selects ASCII hexadecimal digits,
    -- i.e. @\'0\'@..@\'9\'@, @\'a\'@..@\'f\'@, @\'A\'@..@\'F\'@.
    isHexDigit              :: Char -> Bool
    isHexDigit c            =  isDigit c ||
                               (fromIntegral (ord c - ord 'A')::Word) <= 5 ||
                               (fromIntegral (ord c - ord 'a')::Word) <= 5

    -- | Convert a letter to the corresponding upper-case letter, if any.
    -- Any other character is returned unchanged.
    toUpper                 :: Char -> Char

    -- | Convert a letter to the corresponding lower-case letter, if any.
    -- Any other character is returned unchanged.
    toLower                 :: Char -> Char

    -- | Convert a letter to the corresponding title-case or upper-case
    -- letter, if any.  (Title case differs from upper case only for a small
    -- number of ligature letters.)
    -- Any other character is returned unchanged.
    toTitle                 :: Char -> Char

    -- -----------------------------------------------------------------------------
    -- Implementation with the supplied auto-generated Unicode character properties
    -- table

    -- Regardless of the O/S and Library, use the functions contained in WCsubst.c

    isAlpha    c = iswalpha (ord c) /= 0
    isAlphaNum c = iswalnum (ord c) /= 0
    isControl  c = iswcntrl (ord c) /= 0
    isPrint    c = iswprint (ord c) /= 0
    isUpper    c = iswupper (ord c) /= 0
    isLower    c = iswlower (ord c) /= 0

    toLower c = chr (towlower (ord c))
    toUpper c = chr (towupper (ord c))
    toTitle c = chr (towtitle (ord c))

    foreign import ccall unsafe "u_iswalpha"
      iswalpha :: Int -> Int

    foreign import ccall unsafe "u_iswalnum"
      iswalnum :: Int -> Int

    foreign import ccall unsafe "u_iswcntrl"
      iswcntrl :: Int -> Int

    foreign import ccall unsafe "u_iswspace"
      iswspace :: Int -> Int

    foreign import ccall unsafe "u_iswprint"
      iswprint :: Int -> Int

    foreign import ccall unsafe "u_iswlower"
      iswlower :: Int -> Int

    foreign import ccall unsafe "u_iswupper"
      iswupper :: Int -> Int

    foreign import ccall unsafe "u_towlower"
      towlower :: Int -> Int

    foreign import ccall unsafe "u_towupper"
      towupper :: Int -> Int

    foreign import ccall unsafe "u_towtitle"
      towtitle :: Int -> Int

    foreign import ccall unsafe "u_gencat"
      wgencat :: Int -> Int