Greetings, Fellow Monks! The following is my recent conversation with ChatGPT:

Dmitri: What is this regex for?

((?:(?:[^\n@]+|@[^@]*@)\n?)+)
[download]

ChatGPT: This regular expression is used to match a pattern that contains multiple lines of text. The regular expression is designed to match one or more occurrences of a sequence of characters that can include any characters except a newline (represented by \n) or an at sign (@), or an at sign that is immediately followed by one or more other characters (also represented by @) and then another at sign.

The outermost parentheses ( ) define a capturing group that captures the matched text, this group will be repeated one or more times + . The first non-capturing group (?: ) is used to match any characters except a newline or an at sign. The second non-capturing group (?:@[^@]*@) matches an at sign, followed by zero or more characters that are not an at sign, followed by another at sign.

The ? after the first non-capturing group means that the preceding element is optional and can match zero or one time. The ? after the second non-capturing group means that the preceding element can match zero or one time, and the \n means that it will match a new line.

This regular expression should be used in conjunction with other tests or validation to ensure that it only matches valid input. It is not a complete solution to validate emails or other texts, just a pattern matching.

Dmitri: Can you optimize it?

ChatGPT: Yes, it can be optimized for performance. Here's one possible way:

((?:(?:[^\n@]|@[^@]*@)[^\n]*\n?)+)
[download]

• The first change I made is that instead of using \n? after the second non-capturing group, I added [^\n]*\n? which means that the pattern matches zero or more characters that are not a newline, followed by an optional newline. This change allows the regular expression engine to stop looking for a newline as soon as it encounters a character that is not a newline.
• The second change I made is that I used [^\n@] instead of [^\n] before the @ . This change allows the regular expression engine to stop looking for an at sign as soon as it encounters a character that is not an at sign.

These changes should improve the performance of the regular expression by reducing the number of characters that the regular expression engine needs to examine for each match.

However, it's worth noting that regular expressions can be very complex and it's hard to give a definitive answer without knowing more about the specific use case and the input data. You can also try different variations and test them on your specific input to see which one performs better.

---

I think this is pretty good! (The regular expression I picked at random from this old node.)

Have you used ChatGPT? What do you think?

---

---

Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!

Titles consisting of a single word are discouraged, and in most cases are disallowed outright.

Read Where should I post X? if you're not absolutely sure you're posting in the right place.

Please read these before you post! —

• How do I compose an effective node title?
• How do I post a question effectively?
• Markup in the Monastery

Posts may use any of the Perl Monks Approved HTML tags:

a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr

You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)

	For:		Use:
	&		&
	<		&lt;
	>		&gt;
	[		&#91;
	]		&#93;

Link using PerlMonks shortcuts! What shortcuts can I use for linking?

See Writeup Formatting Tips and other pages linked from there for more info.