Scott Hanselman

Internationalization/I18n: Char.IsDigit() matches more than just "0" through "9"

March 10, '04 Comments [5] Posted in ASP.NET | Javascript | Bugs
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Raymond Chen just gave me a "duh" moment, by pointing out the obvious-only-if-you-think-about-it.  Char.IsDigit() doesn't mean 'IsZeroToNineInEnglish', it means 'is in the decimal range of 0 to 9' and darnnit if there aren't other ways (other than 0,1,2,3,4,5,6,7,8,9) to express them! :)

So let's run an experiment.

class Program {
  public static void Main(string[] args) {
    System.Console.WriteLine(
      System.Text.RegularExpressions.Regex.Match(
        "\x0661\x0662\x0663", // "١٢٣"
        "^\\d+$").Success);
    System.Console.WriteLine(
      System.Char.IsDigit('\x0661'));
  }
}

The characters in the string are Arabic digits, but they are still digits, as evidenced by the program output:

True
True
Uh-oh. Do you have this bug in your parameter validation? (More examples..)
If you use a pattern like @"^\d$" to validate that you receive only digits, and then later use System.Int32.Parse() to parse it, then I can hand you some Arabic digits and sit back and watch the fireworks. The Arabic digits will pass your validation expression, but when you get around to using it, boom, you throw a System.FormatException and die.
[Raymond Chen]

Arabic speakers (مرحبًا, كيف حالك ؟ and forgive me, it's been college since I studied Arabic) how to you handle numeric validation in JavaScript AND guarantee that the JavaScript you use on the client-side is semantically equivalent to the server-side code?

Either way, my friends, read, grok, and be enlightened.  Muy interesante.

About Scott

Scott Hanselman is a former professor, former Chief Architect in finance, now speaker, consultant, father, diabetic, and Microsoft employee. He is a failed stand-up comic, a cornrower, and a book author.

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Wednesday, 10 March 2004 11:22:09 UTC
Smart Ass Comment of the Day:

If we all spoke english and used ASCII, we wouldn't have this problem.

Feet
Inches

$0.02

Tower of Babel
Wednesday, 10 March 2004 13:05:53 UTC
Feature Request:

Would there be any remote possibility of adding a feature that would allow posters to delete their own stupid comments? Or edit them? Sort sort of method for self-moderation...

Just a thought...


Wednesday, 10 March 2004 15:14:11 UTC
You may thow up on this, but I would use Web Service Behavior if I really want to guarantee that the JavaScript I use on the client-side is semantically equivalent. You ARE technically using server side logic and it does talk to the server via SOAP behind the scenes, but there were times when it worked perfectly for me.

Yes, you have to also guarantee that all the users use none other than IE. :-)
Wednesday, 10 March 2004 21:48:37 UTC
مرحبا سكوت , كيف حالك انا اتابعك دائما
samdi
Wednesday, 10 March 2004 21:51:48 UTC
Hi scott

How are you , I read your blog , every time
samdi
Comments are closed.

Disclaimer: The opinions expressed herein are my own personal opinions and do not represent my employer's view in any way.