Regular expressions (parse text, find-replace)

Regular expressions are used to parse text: compare, find/get substrings, find-replace, split. Use when you can't get the desired result with simple string functions easily.

This tool can help to create regular expressions: menu Code > Regex. It's like another cookbook.

Although .NET has a regular expression engine (class Regex), the automation library uses another engine - PCRE. It's because some library functions can't use .NET. Both engines are equally powerful and use the same syntax with few unique features. Both can be used in scripts, but with elm functions only PCRE.

The PCRE regular expression class is regexp. And there are string extension methods that use it internally.

• regexp.IsMatch and string.RxIsMatch - compare the string or find a substring.
• regexp.Match and string.RxMatch - compare/find, and get match info.
• regexp.FindAll and string.RxFindAll - find/get all matches.
• regexp.Replace and string.RxReplace - find and replace all.
• regexp.Split and string.RxSplit - split.

var s = "one two22 three333 four";

Find. This example uses a regexp object.

var x = new regexp(@"\b(\w+?)(\d+)\b");
if (x.IsMatch(s)) print.it("found");

This is the same with an extension method.

if (s.RxIsMatch(@"\b(\w+?)(\d+)\b")) print.it("found");

Find and get match info. The m[1] and m[2] are substrings that match regex parts enclosed in ().

if(s.RxMatch(@"\b(\w+?)(\d+)\b", out var m)) print.it(m.Start, m.End, m.Value, m[1].Value, m[2].Value);

Find in part of string.

int from = 8;
if (s.RxMatch(@"[a-z]+", out var mm, range: from..)) print.it(mm);

Find all matches.

foreach(var k in s.RxFindAll(@"\b(\w+?)(\d+)\b")) print.it(k.Value, k[1].Value, k[2].Value);

Find and replace all matches.

var s2 = s.RxReplace(@"\b(\w+?)(\d+)\b", "'$2$1'");
print.it(s2);

Find and replace max 1 match.

print.it(s.RxReplace(@"\b(\w+?)(\d+)\b", "'$2$1'", 1));

Find-replace and get the number of replacements.

int n = s.RxReplace(@"\b(\w+?)(\d+)\b", "'$2$1'", out string s3);
print.it(n, s3);

Find-replace using a callback function.

var s4 = s.RxReplace(@"\b([a-z])(\w+)", m => m[1].Value.Upper() + m[2].Value);
print.it(s4);

var s5 = s.RxReplace(@"\b(\w+?)(\d+)\b", m => m.ExpandReplacement("$1+$2").Upper());
print.it(s5);

Find-replace using a custom function in the replacement string.

regexp.addReplaceFunc("Upper", (m, g, v) => m[g].Value.Upper());
regexp.addReplaceFunc("Add", (m, g, v) => (m[g].Value.ToInt() + v.ToInt()).ToString());

print.it(s.RxReplace(@"\b(\w+?)(\d+)\b", "${+Upper}"));
print.it(s.RxReplace(@"\b([a-z])(\w+)\b", "${+Upper(1)}$2")); //1 is group index
print.it(s.RxReplace(@"\d+", "${+Add(0, 2)}")); //0 is group index, 2 is any value

Split the string.

s = "one, two,three , four";
var a = s.RxSplit(@" *, *");
for(int i = 0; i < a.Length; i++) print.it(i, a[i]);

There are to ways to insert an unknown string into a regular expression:

1. Enclose it in \Q \E.
2. Escape special characters in it.

string c = clipboard.text;
if (s.RxIsMatch(@"...\Q" + c + @"\E...")) print.it("is match");
if (s.RxIsMatch(@"..." + Regex.Escape(c) + @"...")) print.it("is match");