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|
-- |
-- Module : Unicode.Char.Numeric.Compat
-- Copyright : (c) 2020 Composewell Technologies and Contributors
-- License : Apache-2.0
-- Maintainer : streamly@composewell.com
-- Stability : experimental
--
-- Compatibility module for numeric character property related functions.
--
-- @since 0.3.1
--
module Unicode.Char.Numeric.Compat
( -- * Predicates
isNumber
) where
import Data.Char (ord)
import qualified Unicode.Internal.Char.UnicodeData.GeneralCategory as UC
-- | Selects Unicode numeric characters, including digits from various
-- scripts, Roman numerals, et cetera.
--
-- This function returns 'True' if its argument has one of the
-- following 'Unicode.Char.General.GeneralCategory's, or 'False' otherwise:
--
-- * 'Unicode.Char.General.DecimalNumber'
-- * 'Unicode.Char.General.LetterNumber'
-- * 'Unicode.Char.General.OtherNumber'
--
-- __Note:__ a character may have a numeric value (see
-- 'Unicode.Char.Numeric.numericValue') but return 'False', because 'isNumber'
-- only tests 'Unicode.Char.General.GeneralCategory': some CJK characters are
-- 'Unicode.Char.General.OtherLetter' and do have a numeric value.
-- Use 'Unicode.Char.Numeric.isNumeric' to cover those cases as well.
--
-- prop> isNumber c == Data.Char.isNumber c
--
-- @since 0.3.1 moved to Compat module.
--
-- @since 0.3.0
isNumber :: Char -> Bool
isNumber c =
-- NOTE: The guard constant is updated at each Unicode revision.
-- It must be < 0x40000 to be accepted by generalCategoryPlanes0To3.
cp <= UC.MaxIsNumber &&
case UC.generalCategoryPlanes0To3 cp of
UC.DecimalNumber -> True
UC.LetterNumber -> True
UC.OtherNumber -> True
_ -> False
where !cp = ord c
|
