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Working with Strings with Combining Characters

, 30 Mar 2010
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Like diacritics in Arabic, Hebrew, etc.
This article was previously published in my blog, Just Like a Magic.

Contents 

Contents of this article:
  • Contents
  • Introduction
  • Enumerating a String with Only Base Characters
  • Enumerating a String with Combining Characters
  • Comparing Strings
  • Using the Character Map Application
  • Try it out!

Introduction

In some languages, like Arabic and Hebrew, you combine some characters with combining characters based on the pronunciation of the word. Combining characters are characters (like diacritics, etc.) that are combined with base characters to change the pronunciation of the word (sometimes called vocalization.) Some examples of combining characters are diacritics:
Base Character Combining Character(s) Result
1
Combining a single character

Arabic Letter Teh
Arabic Letter Teh
0x062A 

Arabic Damma
Arabic Damma
0x064F
Arabic Letter Teh + Damma.gif
Letter Teh + Damma
2
Combining two characters
Arabic Letter Teh
Arabic Letter Teh
0x062A

Arabic Shadda
Arabic Shadda
0x0651

Arabic Fathatan
Arabic Fathatan
0x064B

Arabic Letter Teh + Shadda + Fathatan
Letter Teh + Shadda + Fathatan
When you combine a character with another one then you end up with two characters. When you combine two characters with a base one you end up with 3 characters combined in one, and so on.

Enumerating a String with Base Characters

Now we are going to try an example. This example uses a simple word,Word Muhammad (Mohammad; the name of the Islam prophet.)

Word Muhammad Details

This word (with the diacritics) is consisted of 9 characters, sequentially as following:

  1. Meem
  2. Damma (a combining character combined with the previous Meem)
  3. Kashida
  4. Hah
  5. Meem
  6. Shadda (a combining character)
  7. Fatha (a combining character both Shadda and Fatha are combined with the Meem)
  8. Kashida
  9. Dal
After characters combined with their bases we end up with 6 characters, sequentially as following:
  1. Meem (have a Damma above)
  2. Kashida
  3. Hah
  4. Meem (have a Shadda and a Fatha above)
  5. Kashida
  6. Dal 

The following code simply enumerates the string and displays a message box with each character along with its index:  

string someName = "مُـحمَّـد";

for (int i = 0; i < someName.Length; i++)
    MessageBox.Show(string.Format("{0}t{1}", someName[i]));
What we get? When enumerating the string, we enumerate its base characters only.

Enumerating a String with Combining Characters

.NET Framework provides a way for enumerating strings with combining characters, it is via the TextElementEnumerator and StringInfo types (both reside in namespace System.Globalization.) The following code demonstrates how you can enumerate a string along with its combining characters:

string someName = "مُـحمَّـد";

TextElementEnumerator enumerator = StringInfo.GetTextElementEnumerator(someName);

while (enumerator.MoveNext())
    MessageBox.Show(string.Format("{0}t{1}", enumerator.ElementIndex, enumerator.Current));

Comparing Strings 

Sometimes, you will be faced with a situation where you need to compare two identical strings differ only by their diacritics (combining characters) for instance. If you were to compare them using the common way (using String.Compare for instance) they would be different because of the combining characters.

To overcome this you will need to use a special overload of String.Compare method: 

string withCombiningChars = "مُـحمَّـد";
string withoutCombiningChars = "محمد";

Console.WriteLine(string.Compare(withCombiningChars,
    withoutCombiningChars) == 0 ? "Both strings are the same." : "The strings are different!");

if (string.Compare(withCombiningChars, 
    withoutCombiningChars, Thread.CurrentThread.CurrentCulture, CompareOptions.IgnoreSymbols) == 0)
    Console.WriteLine("Both strings are the same.");
else
    Console.WriteLine("The strings are different!"); 
The Kashida ـ isn't of the Arabic alphabets. It's most likely be a space! So the option CompareOptions.IgnoreSymbols ignores it from comparison.

Writing Arabic diacritics

The following table summarizes up the Arabic diacritics and the keyboard shortcut for each character:

Unicode Representation Character Name Shortcut
0x064B Arabic Fathatan Fathatan Shift + W
0x064C Arabic Dammatan Dammatan Shift + R
0x064D Arabic Kasratan Kasratan Shift + S
0x064E Arabic Fatha Fatha Shift + Q
0x064F Arabic Damma Damma Shift + E
0x0650 Arabic Kasra Kasra Shift + A
0x0651 Arabic Shadda Shadda Shift + ~
0x0652 Arabic Sukun Sukun Shift + X

Using the Character Map Application

Microsoft Windows comes with an application that help you browsing the characters that a font supports. This application is called, Character Map.

You can access this application by typeing charmap.exe into Run, or pressing Start->Programs->Accessories->System Tools->Character Map.

Try it out!

Code examples for the reader to discover:

A.

string someName = "مُـحمَّـد";

MessageBox.Show(StringInfo.GetNextTextElement(someName,2));



B.

string a = "Adam";
string b = "Ádam";

Console.WriteLine(string.Compare(a, b) == 0 ? "They are the same." : "No, They are different.");

// Also try changing the CultureInfo object
if (string.Compare(a, b, Thread.CurrentThread.CurrentCulture, CompareOptions.IgnoreNonSpace) == 0)
    Console.WriteLine("They are the same.");
else
    Console.WriteLine("No, They are different.");

License

This article, along with any associated source code and files, is licensed under The Common Public License Version 1.0 (CPL)

About the Author

Mohammad Elsheimy
Technical Writer Just Like a Magic
Egypt Egypt
Independent technical writer from Egypt born in 1991.
 
I am a student of The Holy Quranic Sciences Institute. There, we study the Holy Quranic sciences and Islamic legislation.
 
I currently run two sites:
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Comments and Discussions

 
GeneralNot working in .Net 4.0 Pinmemberahmad rabiei zadeh2-Jun-11 0:05 
GeneralThanks - شكرن PinmemberON7AMI18-Oct-10 21:00 
GeneralRe: Thanks - شكرن PinmemberMohammad Elsheimy19-Oct-10 6:04 
GeneralCombiningchars Pinmember@amino23-Mar-10 2:43 
GeneralRe: Combiningchars PinmemberMohammad Elsheimy23-Mar-10 3:43 

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