Data.Char.WCWidth

A binding for the native wcwidth. It's important that you setLocale before using it, like this:

  #!/usr/bin/env runhaskell

  import Text.Printf
  
  import System.Locale.SetLocale
  import Data.Char.WCWidth

  main                     =  do
    setLocale LC_ALL (Just "")
    sequence_ [ display c | c <- chars ]
   where
    chars                  =  [minBound..'A']
    display c = printf "%04x  %2d  %s\n" (fromEnum c) (wcwidth c) (show c)

The program file WCWidthTableaux.hs contains a more extensive example of using wcwidth.

Note that this binding to the native implementation gets certain characters wrong in obvious ways as well as ways that are problematic for indentation based languages. The ASCII tab should be assigned a width of 8, not -1; and one is likely to find -1 assigned to numerous obscure characters (for example, symbols from the Book of Changes).

Documentation

wcwidth :: Char -> Int

Binding to the native wcwidth.

widths :: [(Char, Int)]

Widths of all characters.

ranges :: [((Char, Char), Int)]

Characters broken into contiguous ranges with the same width.