String Operations

Luc Pattyn

Hi, it is not very clear. if you want to split a string s1 using a collection of split characters (say all chars in string s2) and are interested in which split characters actually occur in s1, then this strange snippet offers exactly that; I leave it to the reader to discover how it works!

string[] sa=s1.Split(string.Join("", s1.Split(s2.ToCharArray())).ToCharArray(), StringSplitOptions.RemoveEmptyEntries);

:)

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DaveyM69

Very cool Luc :cool:

Dave
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wasifmuneer

Its Looking Really cool,,thanks for Help but one thing more i have have string array collection, not char array collection,so how can i do this with string array collection..

Luc Pattyn

if you want the result to be a char array, you have to turn my result into a char array; I have already shown how that is done. It is just more of the same stuff. :)

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Dewald

Luc Pattyn wrote:

this strange snippet offers exactly that

neat

Judah Gabriel Himango

I'm glad I don't have to maintain that piece of code. Curious to see what a LINQ-based solution would read like.

Tech, life, family, faith: Give me a visit. The apostle Paul, modernly speaking: Epistles of Paul Judah Himango

Luc Pattyn

The good thing is it doesn't need any maintenance :laugh: ; it could be implemented as an extension method to the string class, I would suggest it gets named RemoveNot(s1,s2): remove all chars from s1 that are not in s2. No idea what LINQ can do here. And also no idea what regex could do (I was surprised no one ever mentioned it so far). I am pretty sure both of them would look even worse, and have lower performance. A lambda expression might come in handy, haven't really considered it (am still working in .NET 2.0) :)

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Guffa

Luc Pattyn wrote:

And also no idea what regex could do (I was surprised no one ever mentioned it so far).

Getting there, just have to read the replies so far first... :)

Despite everything, the person most likely to be fooling you next is yourself.

Guffa

This code will split the string, and give you the result as two arrays; one array with the regular split result, and one array with the splitters that was used. The usedSplitters array is one item shorter than the words array. If no splitters were found, the words array contain the original string, and the usedSplitters array is empty.

string source = "asdf,asdf;;;asdf,asdf::asdf..asdf";
string[] splitters = { "..", ",", ";;;", "::" };

string pattern = "(" + string.Join("|", splitters.Select(s => Regex.Escape(s)).ToArray()) + ")";
MatchCollection matches = Regex.Matches(source, pattern);
string[] words = new string[matches.Count + 1];
string[] usedSplitters = new string[matches.Count];
int pos = 0;
for (int i = 0; i < matches.Count; i++) {
words[i] = source.Substring(pos, matches[i].Index - pos);
usedSplitters[i] = matches[i].Value;
pos = matches[i].Index + matches[i].Length;
}
words[matches.Count] = source.Substring(pos);

Despite everything, the person most likely to be fooling you next is yourself.

Luc Pattyn

I'll hold the line

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Luc Pattyn

I like the concept, my Visual Studio targetting 3.5 does not know the Select method though. Anyway, it is not one of those obscure regex applications... :)

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Guffa

I think that you need using System.Xml.Linq; to get the Select extension. Here's a way to create the pattern without it:

StringBuilder builder = new StringBuilder().Append('(');
bool first = true;
foreach (string s in splitters) {
if (first) {
first = false;
} else {
builder.Append('|');
}
builder.Append(Regex.Escape(s));
}
string pattern = builder.Append(')').ToString();

Despite everything, the person most likely to be fooling you next is yourself.

Luc Pattyn

the original works like a charm once I added using System.Linq; Without Select, I would write

StringBuilder builder = new StringBuilder().Append('(');
string sep="";
foreach (string s in splitters) {
builder.Append(sep).Append(Regex.Escape(s));
sep="|";
}
string pattern = builder.Append(')').ToString();

avoiding the extra state variable and if-else test. Thanks. :)

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Guffa

Is it better? You are just replacing one state variable with another, making the value of the variable double as both state and value. :)

Despite everything, the person most likely to be fooling you next is yourself.

Luc Pattyn

I trust this is subjective, however I see lots of small reasons, yes: I find it shorter, more readable, less error prone, and possibly better for instruction scheduling. Also for testing and proofing correctness avoiding if-tests generally is beneficial. :)

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realJSOP

If you mean that you want to get the string that was originally split from the array, you will either have to write a method to do that, or you can use my handy-dandy string parsing class, available here[^] on CodeProject.

"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass..." - Dale Earnhardt, 1997
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