Haskell, Char, Unicode, and Turkish

Question

For the Char data-type, how do I specify that I want to use the Turkish i instead of the English i for the toLower and toUpper functions?

Answer 1

text and the text-icu package

As of 2011, your best bet is to use the text package, and the toLower function of the Text ICU package, which supports Char operations parameterized by a locale,

From this example:

import Data.Text (pack, unpack)
import Data.Text.ICU (LocaleName(Locale), toLower)

main = do
  let trLocale = Locale "tr-TR"
      upStr    = "ÇIİĞÖŞÜ"
      lowStr   = unpack $ toLower trLocale $ pack upStr
  putStrLn $ "toLower " ++ upStr ++ " gives " ++ lowStr

Running this:

> toLower ÇIİĞÖŞÜ gives çıiğöşü

while this example converts between String, you can also just leave the data in text format.