C++ Tutorial 19 : C++ Regular Expressions

[@ngneer5804]

Old video, but in case anyone watches it, there are some mistakes: 1. std::smatch::size() does not return the number of matches! it returns the number of capture groups plus 1 for the whole match! The reason he gets 2 is because he put the whole string inside a capture group (round brackets). So one for the whole match, and one for the capture group. If he'd use another set of these brackets, he'd get 3. 2. std::smatch::str(1) does not return the first match! it returns the first capture group! 0 is the whole match, but because he put the whole string inside a capture group, using 0 would net him the same result as 1. 3. \w also matches an underscore (_), and naturally, underscore wouldn't be matched with \W (i.e. capital letter w). In general, using capturing groups (round brackets) is expensive and shouldn't be used if there's no point for it, and in this video there really wasn't a point. Even if you need to use parenthesis, you can disable capturing by adding ?: in the beginning. No disrespect to the author by the way! The video was decent overall!

[@gigamungus5764]

I have an interview coming up in a few days for c++ and a week ago i had never even looked at the language, you have no idea how grateful I am that you started making this when you did

[@derekbanas]

Thank you :) I'm happy I could help. Best of luck on your interview

[@abeerkh4493]

Thank you so much for your hard work on your videos. I have learned more from you than my university doctors. The way you explain stuff in a very simple and straight forward way is AMAZINGGGG. I really appreciate your efforts. THANK YOUUUU

[@derekbanas]

Thank you for taking the time to tell me I helped :) I'm very happy you are enjoying my videos

[@vojar3692]

Huge appreciation for your determination, free educational videos and effort to help everyone! Hope your 2019 is gonna be ++awesome! All the best!

[@derekbanas]

Thank you very much :) I wish you all the best in the new year!

[@justsurajp]

At 26:48, wouldn't the "." (dot) accept any character instead of period character? Would it be more meaningful to use "\\." instead to specify we are looking for a period and not just any character?

[@gigamungus5764]

in the final example you didn't escape the dot, so it was matching any character, not just "."

[@derekbanas]

Whoops sorry for the typo. I wrote the code largely out of my head

[@jonajo261]

I don't undestand, in PrintMacht2 you don't initialize lastMach wtf is going on ; how can you check for the value if lastMatch is empty

[@samitkapoor53]

at 26:50 wont we add another '\' before '.' to escape the '.' in reg14?

[@Skooma150]

Thanks for this video. Been a while since I used regex and the syntax is very confusing, especially when you're rusty. Spent hours on stack and this is the first thing that helped me make any progress.

[@sabrinanastasi5809]

Hands down the best regex tutorial, thank you!!!!

[@exodus8814]

This is wonderful :) Thank you very much Derek, you never fail to upload such high quality and clear videos, you are awesome! Thanks :)

[@derekbanas]

Thank you for the nice compliment :) I try to do my best

[@exodus8814]

Derek Banas Wow thanks for the fast reply too :)

[@feraudyh]

There's one thing I did not get: lastmatch is not set anywhere, so why should it represent the end?

[@shawnarmstrong3339]

I looked into this. The default constructor for sregex_iterator creates an end-of-sequence iterator; from the documentation : "The default-constructed std::regex_iterator is the end-of-sequence iterator. When a valid std::regex_iterator is incremented after reaching the last match (std::regex_search returns false), it becomes equal to the end-of-sequence iterator. Dereferencing or incrementing it further invokes undefined behavior."

[@jamesday2386]

@@shawnarmstrong3339 life saver, thank you

[@bryany3241]

Don't you need to use double backslashes in c++ regex, to escape the escape character (the backslash)?

[@nicklansbury3166]

Derek, as always, another very informative tutorials. Thanks for that. I was wondering. Now that you've done a 'How to Make Video Games' series and you are currently doing a 'C++ Tutorial' series, would you consider combining the two subjects? I'd love to see a 'How to Make Video Games using C++' series. Just a thought.

[@kesuskim6072]

yeah, possibly using Unreal engine or SFML!

[@nicklansbury3166]

Actually I'd prefer to do something 100% in code rather than use a visual editor. There's already a ton of UE4 tutorials around. Getting down and dirty with the code is what interests me.

[@derekbanas]

I'll see what I can do. I can make a basic graphics engine and if people watch it I'll continue making videos. I love covering complex topics, but they are a double edged sword. They are harder to make and then it is disheartening after I make one to see that only 20 people watched the whole video.

[@derekbanas]

I'm working on a UE4 tutorial

[@kesuskim6072]

wow, making basic graphics engine!! :) very interesting derek, I'm very interested (y)

[@muhsenalkhalidy7849]

Hello , i included the regex library and when type std::smatch sm; the compiler gives error says that smatch is not a memeber of std? plz help

[@MatthewBendyna]

Does the carrot symbol still mean begins with in C++ like in Python and C# when not inside the brackets? (assuming brackets mean set)

[@shreyshah4220]

Great video! Just use the "using namespace std" at the start! It is really off putting.

[@MrinmoyHaloi]

i have a problem where i need to use the dotall flag. How can i do that in c++ ?

[@Omar-dd2lw]

i study programming in college ,and cause of your videos i just got 60/60 (full mark) in C++ ,thank you so much

[@derekbanas]

Awesome! Great Job :)

[@MochrieTVHotS]

Fantastic video! :) The length is absolutely justified by the content.

[@derekbanas]

Thank you very much :)

[@russellmcnamara6107]

Derek I am your biggest fan my name is Russ I have been in jail for a year and I could never stop thinking about you and your videos they're so amazing I couldn't stop about how you said hello Internet and everything about your videos and you I hope your doing good I love your videos so much

[@bobhutchinson3638]

Seems like you are okay for now!

[@jakesmith6853]

As usual, big thanks to you :). Preparing for a tech interview with the help of your videos. You rock!

[@derekbanas]

Thank you very much :) I wish you the best of luck on your interview!

[@ashleyrawr74]

Hi, I'm trying to use the iterator but I'm getting a "regex_iterator not dereferencable" bug message in output. Any ideas on how to fix this?

[@derekbanas]

I have working code in the description. Try comparing it to yours using diffnow.com

[@limyautito3298]

How can I use the regex library?

[@gnujeu]

I just wanted to say I figured out the application... Your videos are very helpful

[@derekbanas]

I'm happy I could help :)

[@kholiyamails1257]

there was the question by amazon related regular expression ........ if starting char match with last char (example : aba , ab , aa) aba and aa would be true and I was given only this line regex regular_expression("________________") ,and I only was to write inside it ,so what should be written inside it .🙂

[@alonsamuel934]

Hi!! Thank you very much for the tutorial!! it helped me understand some basic ways to use regex in order to shorten my life in searching string stuff. :) I wanted to ask how did you use currentMatch? I thought that you would first declare it as an iterator and then fill it with data. I didn't see where did you put data in it... I also didn't understand how did you declare it with parenthesis ? If you could explain a bit more for me... thank you !!

[@GeckoSharky]

"Any call to regex_match or regex_search with the match_results object as argument sets this value to true, even if the function does not succeed in finding any match." You sure that ready() indicates that there is a match or not? Doesn't sound like it according to the docs.

[@derekbanas]

Thank you for pointing that out. I bungled my explanation. It returns true if the test for results is finished. I updated the code on my site.

[@terrylim4725]

Around the 17min mark of your video: Using: std::regex reg7 ("([^ ]\..\..\.)"); Gave this error: warning: unknown escape sequence: '\.' Changing the line to : std::regex reg7 ("([^ ]\\..\\..\\.)"); resolved the error, and the code could compile

[@abderrazakschannel4491]

how to do the apostrophe in regex?

[@AdityaDodda]

In PrintMatches the number of matches seems to be incorrect. Try setting std:regex reg("(was)"); The number of matches evaluates to 2.

[@samng1158]

yeap, there is an error. not sure why might be the pattern

[@NicoScholz90]

makes me wonder as well. Anybody got a clue what exactly goes wrong here?

[@exodus8814]

Hey Derek! I have a suggestion, could you please think about doing compiler videos? That would be insane!

[@derekbanas]

Compilers aren't really that complicated. You basically have to translate from one language to another. Making an optimized compiler is the hard part

[@exodus8814]

Derek Banas thank you very much for response, sorry if I asked too many questions. :)

[@marianacsinlove]

There's no need to declare de functions printmatches??

[@Sebastian-qc3gw]

Hi, thanks for the tutorial, helped me a lot! I think reg7 should be "([^ ]\\..\\..\\.)". In this particular case it works, but if str7 was "F.B.I. I.R.S. CIA F.B.I." the output doesn't meet the expectations.

[@jacktolmie1971]

Thanks. I was wondering why I was getting warnings. I was looking through the comments for an answer to this exact issue :).

[@vnm_8945]

Can I ask how many tutorials will be added to complete this C++ tutorial and when this is going to happen, some estimation?

[@derekbanas]

Sorry I don't know. I'll continue making tutorials until I feel I've covered most everything

[@vnm_8945]

Ok, thank you, I'm interested in linked list, I will watch all the videos, but I don't think it's covered. I'm learning something new in every video, thank you for the effort.

[@cerrillotorrescarlosivan5442]

Muy buen video amigo, una duda, en el regex siempre se debe introducir la expresión a evaluar o hay alguna forma de hacer uso de regex pero que no se defina la expresión, si no que el usuario la introduzca?

[@timothyleffel3186]

thanks for making the internet a less icky place

[@derekbanas]

I'm trying to do my best :)

[@akagaming9431]

Yeah, it's about goddamn time we have this tutorials haha :D I've been waiting for your C++ videos and it feels like ages, thanks for the tutorials Derek!

[@derekbanas]

I'll do my best to get them out quicker. Work has been crazy lately. Maybe someday I can do this full time :)

[@levhordiichuk6651]

Hi, you used ' \. ' in F.B.I. ex. and said that if i want to search ' . ' i must use ' \. ' and then in 'homework' you did not use ' \. ' . Can you explain why? Or you just made a mistake? Thanks. P.S. tutorial is really helpful.

[@shinwarivideos3356]

sir I need this Odd length regular expression implementation in c++

[@adamchalkley956]

I wouldn't call this a tutorial,because well it's not really,I would call it a refresher. You don't actually take time to explain whats going on instead you just write code assuming we already know what the function does,what it returns and how the functions you are using work.

[@kedicat7]

Functions are explained here kzbin.info/www/bejne/baGvnZecj9qhgKs it is 10 -15 chapter before. (I am not Derek's friend or something but ...he explains it very well here. )

[@JoeGlines-Automator]

Regular Expressions rock! Thanks for this inspiring tutorial! I've made a few on it but enjoyed watching yours as well! :)

[@derekbanas]

I'm very happy you liked it :) Thanks for taking the time to tell me

[@larrybishop5139]

Hey Derek great video. I just have another question though. In your long c++ tutorial i saw you use some type of syntax. Is it better to use getline or just the regular cin?

[@derekbanas]

Thank you :) Sometimes you have to use getline, but often they are interchangeable. For example we are receiving input here std::cout

[@larrybishop5139]

Ok thank you.

[@JustinK0]

Nice, Right out of ch 17.3 in the c+ Primer textbook that i read right before this video! haha

[@junfengwei8877]

Hi,what is your ide? Vs code+clang

[@_________________404]

He's using netbeans. But I don't think it's the best IDE to use, he just uses it because he's on a Mac.

[@crystyxn]

Hey great vids on c++. How long will this series be ? Please make one about making your own C++ library soon! Or if you know any resources you could redirect me to thanks

[@derekbanas]

I'm not certain. I covered how to include outside files here kzbin.info/www/bejne/r6ixi3Sbl8x4kNk

[@2271masoud]

Thanks for the tutorial Derek. I wish I could upload the photo I took of the screen with your name on top saying the best channels on KZbin. it happened in the biggest javascript meetup here in London. Thanks for all your efforts

[@derekbanas]

Wow that is amazing!!! Thank you for telling me :) I've personally never met anyone that has watched my videos. It is always nice to hear that they have helped

[@Omar-dd2lw]

yaaaaay a c++ video , love you

[@derekbanas]

I'm glad you liked it :)

[@neerajsingh769]

Please upload some video on advance internet technologies and web security based on java , servelets, ejb etc. Including xml...thanx

[@brodypaterson6695]

Hey Derek, I’ve been watching your videos for a while now, and I would like to know if you’d be open to making a how to make a desktop computer series. I hope you see this. Thanks your a great KZbinr and I love your videos.

[@derekbanas]

Thank you for the nice compliment :) That isn't really my area of expertise and I'm also pretty cheap. I normally buy everything refurbished and buy old models. My current computer is 5 years old.

[@brodypaterson6695]

Derek Banas ah ok thanks for the response.

[@HellHappens]

The internet was made to have such great information spread! Do you think you could cover MTAs on Linux? It is the most confusingly documented software I've ever seen. Exim would be nice but honestly I just want some help setting up custom emails

[@derekbanas]

Thank you :) Do you want a mail server?

[@HellHappens]

Well it's a long story. I have an odd boss who wanted to set up his own business, email server included. He basically said figure it out and I knew next to nothing about linux. He was then convinced Qmail was the way to go and for 5 months we tried messing with it to no avail via our ineptitude. We switched OS's three times from an older version of fedora, to the newest, to CentOs. then went with Exim. Got it half running, ran into an ssl certificate error and could only send emails to ourself. It has been quite the en devour and basically no tutorials exist that don't expect you to have a decent background in running things. I've always been avoidant when it comes to asking for things because I find it rude, but I would LOVE absolutely love an exim centos tutorial or any Mta/mail server tutorials. So Much love ~R

[@Rashaadthegr8]

How do I use this in mac? Seems like the setup different then using virtual machine and visual studio.

[@derekbanas]

I show how to install everything in this video kzbin.info/www/bejne/epLQpnhuibJmrtE

[@exodus8814]

Hello again Derek, (leaving a new comment instead of a reply to insure that you get this), I've seen a reply of yours stating that you would do a simple graphics engine, my question is do you prepare/study before making such complicated topics? Or do you write them out of your head? I would love to be like this, is it possible to reach that point?

[@derekbanas]

I'd research to make sure there aren't better ways then I currently know. I'm nothing special. Anything I do anyone else can do. I can't stress that enough.

[@exodus8814]

Derek Banas Yes you are :) You're an inspiration and a very smart person Derek:) May God bless you and your family.

[@derekbanas]

May God bless you and your family as well :)

[@angadminhas7207]

Can you do one for swift 4?

[@derekbanas]

I'll see what I can do

[@AbhiRadhikaDas]

Thanks man!

[@kedicat7]

Thank you a lot, it is not easy to find good tutorials for c++ regex.

[@derekbanas]

I'm happy I could help :)

[@nikhiledu7556]

I was little worried 😂 coz you didn't post for a while. Thanks✌️

[@derekbanas]

Sorry for the wait. I was a little overwhelmed with work last week. I should be able to make a bunch of videos this week.

[@theoathman8188]

I have noticed that Regular Expressions are extremely slow and produce a massive assembly code. So if you can get away with it, please do.

[@j055116]

Thank you very much! It helps me a lot.

[@derekbanas]

I'm happy you found it useful 😁

[@bruh-moment-21]

very helpful! thank you!

[@derekbanas]

Thank you :)

[@joeflynt7480]

Okay so I dont mean this in a mean way so I hope if he ever reads this he doesnt take it that way but this guy sounds like the head pixie from fairly oddparents to me

[@derekbanas]

That's funny :)

[@akj7]

Thanks man.

[@derekbanas]

Happy to help :)

[@thebeginningk8944]

Thank you very much

[@derekbanas]

I'm very happy to be of help :)

[@talha_coding_tutor]

i used chat gpt for this std::regex singleOperandPattern(R"(^(\w+)\s+(-?\d+(\.\d+)?))"); std::regex doubleOperandPattern(R"(^(\w+)\s+(-?\d+(\.\d+)?),\s*(-?\d+(\.\d+)?))"); can someone explain this to me !

[@V1kToo]

Should have started with a very simple sentence instead of using a whole function.

[@sayedrenaq7747]

6:45

[@ElMachoOpresor]

20:52

[@ПашаХЗ-м8й]

Это не все!

[@shivamraj2649]

Finally

[@derekbanas]

Sorry for the wait

[@Alphabet_-_]