CODEWITHSUNDEEP
c#.netunicode.net-4.0
Royi Namir
Royi Namir

Reputation: 148524

Reverse a string with accent chars?

So I saw Jon's skeet video and there was a code sample :

There should have been a problem with the é - after reversing but I guess it fails on .net2 (IMHO), anyway it did work for me and I did see the correct reversed string.

char[] a="Les Misérables".ToCharArray();
Array.Reverse(a);
string n= new string(a);
Console.WriteLine (n); //selbarésiM seL

But I took it further:

In Hebrew there is the "Alef" char : א

and I can add punctuation like : אֳ ( which I believe consists of 2 chars - yet displayed as one.)

But now look what happens : 

char[] a="Les Misאֳrables".ToCharArray();
Array.Reverse(a);
string n= new string(a);
Console.WriteLine (n); //selbarֳאsiM seL

There was a split...

I can understand why it is happening : 

Console.WriteLine ("אֳ".Length); //2

So I was wondering if there's a workaround for this kind of issue in C# ( or should I build my own mechanism....)

Upvotes: 26

Views: 4705

Answers (2)

Jodrell
Jodrell

Reputation: 35716

If you made the extension

public static IEnumerable<string> ToTextElements(this string source)
{
    var e = StringInfo.GetTextElementEnumerator(source)
    while (e.MoveNext())
    {
        yield return e.GetTextElement();
    }
}

you could do,

const string a = "AnyStringYouLike";
var aReversed = string.Concat(a.ToTextElements().Reverse());

Upvotes: 11

Michael Liu
Michael Liu

Reputation: 55389

The problem is that Array.Reverse isn't aware that certain sequences of char values may combine to form a single character, or "grapheme", and thus shouldn't be reversed. You have to use something that understands Unicode combining character sequences, like TextElementEnumerator:

// using System.Globalization;

TextElementEnumerator enumerator =
    StringInfo.GetTextElementEnumerator("Les Misאֳrables");

List<string> elements = new List<string>();
while (enumerator.MoveNext())
    elements.Add(enumerator.GetTextElement());

elements.Reverse();
string reversed = string.Concat(elements);  // selbarאֳsiM seL

Upvotes: 41

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