How to make a delimiter in c# and take the value

Question

C# Visual Studio 17

Just assume I have a string which has the value [3-4+6*2] or even [3-4+20-0.5] ... and I want them to be stored in a string array... I've researched and found that using split, trim start, trim end We can separate them...

.TrimStart('[')
.TrimEnd(']')
.Split('-','*','+');

But I was unable to find whether we can do this I mean

But I couldn't find anywhere how to store the delimiters too but have them do their work(i meant separating)!!

The value stored will be { 3, 4, 6, 2 } but I want this { 3, -, 4, +, 6, *, 2 } and what do I do with the extraordinary zeroes!!!?

Answer 1

In general case, you have to use a parser; if want just to split and preserve the delimiter, please, have a look at Regex.Split:

  string source = "[-3*4+20-0.5/-4.1]";

  //TODO: specify the delimiters:
  // If you want more delimiters, e.g. (, ), [, ] etc. 
  // for, say, 9*[(456+789)/(95-2.96)-3]
  // just add them into the array
  char[] delimiters = new char[]  { '*', '+', '-', '/' };

  string pattern = "(" + string.Join("|", delimiters
    .Select(item => Regex.Escape(item.ToString()))) + ")";

  string[] result = Regex
    .Split(source.TrimStart('[').TrimEnd(']'), pattern) // (...) preserves delim
    .Select(item => item.Trim()) // <- if you want to trim each item 
    .Where(item => !string.IsNullOrEmpty(item))
    .ToArray();

  // -, 3, *, 4, +, 20, -, 0.5, /, -, 4.1
  Console.Write(string.Join(", ", result));

Edit: For large texts you may want to implement the Split manually:

public static List<string> SplitPreserveSeparators(string source, char[] delimiters) {
  if (null == source)
    throw new ArgumentNullException("source") 
  else if (delimiters == null)
    throw new ArgumentNullException("delimiters") 

  int start = 0;
  int index = -1;

  List<string> items = new List<string>();

  while ((index = source.IndexOfAny(delimiters, start)) >= 0) {
    string value = source.Substring(start, index - start);

    if (!string.IsNullOrEmpty(value))
      items.Add(value);

    items.Add(source.Substring(index, 1));
    start = index + 1;
  }

  if (start < source.Length)
    items.Add(source.Substring(start));

  return items;
}

And use it

string source = "[-3-4+20-0.5/-4.1]";
char[] delimiters = new char[]  { '*', '+', '-', '/' };

List<string> result =  SplitPreserveSeparators(
  source.TrimStart('[').TrimEnd(']'),
  delimiters);

Console.Write(string.Join(", ", result));