Using Regular Expressions - Computerphile

Professor Brailsford takes the theory of RegEx and puts it into practice.


This video was filmed and edited by Sean Riley.

[ashishacharya]

I wish I could have a long and deep conversation with Professor Brailsford over an afternoon tea. He's so Jolly.

[malksc]

Obligatory xkcd:
"I have a problem. I know, I'll write a regexp for it! Now I have two problems."

[SudaNIm]

I’m really enjoying these videos; My knowledge of RegEx is entirely practical, and limited to contemporary uses for string validation, matching, and parsing. I had presumed some ultimate shared origin with lexical grammar theory, but I had no idea it was so diverse and fundamental.

[tomvleeuwen]

4:21 The video-editor is clearly less experienced with regex, leaving out the essential asterisk...

[lawrencedoliveiro]

Some people, faced with the problem of comprehending a presentation on regular expressions, like to distract themselves with a well-known and overused Jamie Zawinski quote. Now they have two problems ...

[userou-igze]

please a more in-depth regex part 2 video!! Vote up if agree!

[BergenVestHK]

Professor Brailsford always brightens my day. Thank you so much!

[steveger]

To get close and personal with regular expressions, I would recommend the command line tools egrep (for searching text) and sed (to search and replace text). Both deliver immediate results and are very useful and versatile tools in their own right.

[PopeLando]

Here's a little unexpected connection. My favourite little function that I wrote is to convert any number into its Roman numerals. And I used both recursion AND regexes to do it! It's nice that these are both areas Prof. Brailsford is the Numberphile expert on, because I'm such a huge fan.

[pianochannel]

I just finished building a lexer and a parser in C for a new programming language. I'm here to listen to the professor more than anything else.

[suicidalbanananana]

Next video should be about RFC5322 and how insane regex can become (to a point where its actually quite terrible for what most people use it for)

[wakiilcaashaq]

Am actually doing this in this semester and the prof is really teaching superbly.

[laxrrs]

When I worked at Yahoo! years ago my Boss used to quip, "regular expressions are anything but regular."

[ZipplyZane]

I use regex mostly to search existing strings. It will allow me to capture portions of data, replace data, or simply tell me if the string is okay.

And it works just fine for this both in userscript and when searching a document.

I actually don't know why else you would use it, nor why it would be bad in this context.

[Ceelvain]

Does lex (or flex) compile a full blown determinitstic automaton with the union of all the regexes? Or does it try them all in sequence?
Both approaches have their pros and cons.

[jaspervaldivia]

I would to be enrolled in one of his classes, or to help with his research. A truly inspiring and engaging professor, I am sure.

[deidara_]

Honestly I feel like windows 7 is better, at least I don't get pestered with update notices every 15 minutes, and the UI is just so much clearner and intuative, not to mention that windows 10 comes with half the drive filled with adware, a lot of it is near impossible to uninstall. If security is of concern, use Linux.

[kurtu]

Regex can't cope? Thats AWKward.

[iamTheSnark]

I still use TSE (The Semware Editor) which lets me use regular expressions in its script language. Works for me.

[andrewwmitchell]

Oh my goodness, that's Principles of Compiler Design next to his monitor. Wow, that was one of my Computer Science textbooks, last century.