content: {-# 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
  
  