ucd-0.0.1.2: src/Data/Char/Properties/BidiBrackets.hs

module Data.Char.Properties.BidiBrackets (Type (..), paired) where

import Control.Monad (guard)
import Data.Bits
import Data.Bool
import Data.Int
import Data.Word

foreign import ccall unsafe "bidi_brackets" c_bidi_brackets :: Word32 -> Word32

data Type = O | C
  deriving (Eq, Read, Show, Enum, Bounded)

paired :: Char -> Maybe (Char, Type)
paired x = (toEnum $ fromEnum x + d, bool O C $ testBit x' 31) <$ guard (d /= 0)
  where
    x' = c_bidi_brackets (fromIntegral (fromEnum x))
    d = fromIntegral $ shiftR (fromIntegral (shiftL x' 1) :: Int32) 29
{-# INLINE paired #-}