使用正则表达式拆分模式

Question

I am new to using pattern in regular expression. I have read a couple of links from Microsoft site, thought I understood but I came across this scenario and do not know why it is not providing the results I expected.

I would like to split MyCmd into a list of strings: print,a,+,b,; Normal split will not keep the delimiters as far as I understand. So, I think I have tried using regex with the pattern defined below: (basically I want to split the string into a list or queue and keep the delimiters ;,+-*/{}[]).

 string MyCmd = "print a+b;";
 private string MyDelim = @"\b[\s;,\+\-\*\/%=\<\>\(\)\{\}\[\]]\w+";
 myStuff = new Queue<string>(Regex.Split(MyCmd,MyDelim));

But so far, my code above is not yielding the expected results.

What is not correct in my pattern?

Answer 1

I believe you can use

var MyCmd = "print a+b;";
var MyDelim = @"([][\s;,+*/%=<>(){}-])";
var myStuff = Regex.Split(MyCmd,MyDelim).Where(p=> !string.IsNullOrWhiteSpace(p)).ToList();

Output: print , a , + , b , ;

Note that the ([][\\s;,+*/%=<>(){}-]) regex is enclosed with (...) and that capturing group makes sure the captured values also get added to the resulting array.

You need the .Where(p=> !string.IsNullOrWhiteSpace(p)) to get rid of empty values that you will get with Regex.Split .

I removed excessive escaping in your regex so that it looks "lean and mean".

The reason your regex does not work is that @"\\b[\\s;,\\+\\-\\*\\/%=\\<\\>\\(\\)\\{\\}\\[\\]]\\w+" matches the spaces and symbols in the character class after a \\b word boundary (requiring a word character to appear before them) and then it matched one or more word characters. Since there is no capturing group, all the matches disappeared from the resulting array.

Answer 2

Regex.Split is the way to go. If using Regex.Matches , you can do like this:

string MyCmd = @"print  a+b;";
string MyDelim = @"([^;,+\-*/{}\[\]\)\(\s]+|[;,+\-*/{}\[\]\)\(])";
var myStuff = Regex.Matches(MyCmd, MyDelim).Cast<Match>().ToList().ConvertAll(m => m.Groups[1].Value.ToString());