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Accepted
F. Iván
Asked: 2020-09-16 22:24:41 +0800 CST 2020-09-16 22:24:41 +0800 CST

How to preserve delimiter when using string.Split()?

  • 772

Suppose we have a string that represents an equation:

string ecuacion = "x^4-x^3-5x^2-x-6";

And we want to get the space between the operators:

char[] operadores = new char[] { '-', '+', '*', '/' };

If we use string.Split();to separate the modules from each other in a list in the following way:

List<string> subEcuaciones = new List<string>();
subEcuaciones = ecuacion.Split(operadores, StringSplitOptions.None).ToList();

The result we get is:

x^4
x^3
5x^2
x
6

However I would like to preserve the operator by which they are delimited, i.e. get as a result:

 x^4
-x^3
-5x^2
-x
-6

Is there a setting to preserve the operators?

c#

2 Answers

  1. It is best to use a regular expression as it split does not maintain the delimiter.

    In the following example I show you how it would be done usingRegex.Split

            string ecuacion = "x^4-x^3-5x^2-x-6";
        char[] delimitadores = new char[] { '-', '+', '*', '/' };
        string delimitadoresunidos = System.Text.RegularExpressions.Regex.Escape(string.Join("", delimitadores));

        string[] Separado = System.Text.RegularExpressions.Regex.Split(ecuacion, "([" + delimitadoresunidos + "])");

        for (int i = 0; i < Separado.Length ; i++)
        {
            Console.WriteLine(Separado[i]);
        }

    Result

    x^4
-
x^3
-
5x^2
-
x
-
6
    • 2
  2. Best Answer

    How to preserve the delimiter when using string.Split()?

    It is not preserved. And that's the expected behavior of string.Split(), according to the documentation :

    Split is used to split a delimited string into substrings. You can use a character array to specify zero, one, or more delimiter characters (the Split(Char[])method), or you can use a character array to specify zero, one, or more delimiter strings.

    That is, you use Split to split a string, you don't need delimiters. In fact, in your case, what you call a delimiter is not such, the symbols you mention have a semantic meaning for each of the subexpressions of your string, they do not have a delimiter meaning .

    Take a look at this question where someone is faced with the same exercise you expose.

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