Question

I have a Regex to split out words operators and brackets in simple logic statements (e.g. “WORD1 & WORD2 | (WORd_3 & !word_4 )”. the Regex I’ve come up with is “(?[A-Za-z0-9_]+)|(?[&!\|()]{1})”. Here is a quick test program.

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using System; 
using System.Text.RegularExpressions;

namespace ConsoleApplication1 
{ 
    class Program 
    { 
        static void Main(string[] args) 
        { 
        Console.WriteLine("* Test Project *"); 
        string testExpression = "!(LIONV6 | NOT_superCHARGED) &RHD"; 
        string removedSpaces = testExpression.Replace(" ", ""); 
        string[] expectedResults = new string[] { "!", "(", "LIONV6", "|", "NOT_superCHARGED", ")", "&", "RHD" }; 
        string[] splits = Regex.Split(removedSpaces, @"(?[A-Za-z0-9_]+)|(?[&!\|()]{1})");

        Console.WriteLine("Expected\n{0}\nActual\n{1}", expectedResults.AllElements(), splits.AllElements());

        Console.WriteLine("*** Any Key to finish ***");
        Console.ReadKey();
    }
}

public static class Extensions
{
    public static string AllElements(this string[] str)
    {
        string output = "";
        if (str != null)
        {
            foreach (string item in str)
            {
                output += "'" + item + "',";
            }
        }
        return output;
    }
}

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The Regex does the required job of splitting out words and operators into an array in the right sequence, but the result array contains many empty elements, and I can’t work out why. Its not a serious problem as I just ignore empty elements when consuming the array but I’d like Regex to do all the work if possible, including ignoring spaces.

Answer 1

var matches = Regex.Matches(removedSpaces, @"(\w+|[&!|()])");

foreach (var match in matches)
    Console.Write("'{0}', ", match); // '!', '(', 'LIONV6', '|', 'NOT_superCHARGED', ')', '&', 'RHD', 

Actually, you don’t need to delete spaces before extracting your identifiers and operators, the regex I proposed will ignore them anyway.