Advanced C++: const and Functions

There are 3 ways a const can be used with a function:
1. const parameter;
2. const return value;
3. const function.
Notes can be downloaded from: boqian.weebly.com

[@thachnnguyen]

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[@sandeepkalwale7707]

Very clear and unique content. All important concepts covered through series. Thanks for your valuable contribution. Please prepare more playlist on C++.

[@YM-vn2ts]

One of the best C++ videos on youtube. Thank you

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Awesome videos !!!! Clear explanations better than going through books!

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[@riwawaves]

no wonder i was so confused, my professor introduced this week 2 into the course. tysm for the clear explanation!

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you have a good clarity on separation of concerns.. good job

[@plutonnico1733]

MANY THANKS BO QIAN!! Subjects are very good, explanation too!

[@toth1982]

8:00 This behavior that when we overload a member function with cost is something which can lead to unexpected errors imho. Suppose you writer of the class writes a const variant. It will run for non-const object. Then the writer of the class writes a non-const variant. From now on the new (non-const) function will be called for the same call. For me this can lead to unexpected errors.

[@oualice9410]

Clear logic with concise examples. Great video!

[@00gamer2]

I think "passive function" would be more appropriate name for const functions; constant variables keep the internal state of themselves constant though out. They are only worried about themselves; they don't care if they change the state of an external variable. Const functions differ in this respect. If const variables are children, then the functions are carers, always making sure the function and variables that are in their care are not hurt in any way. These const functions _care_ about others, you see. They are unsung heroes of this great paradigm of programming that we call "C++", because they CARE. _THEY CARE_. Calling these role-models "const functions" is an insult! They are _not_ children, _not_ those egotistic const variables playing it safe! To express my respect for these functions, I shall, from now on, call them: "mother functions". *THE TRUTH HAS BEEN SPOKEN*

[@SkSafowan]

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[@МаратСаидов-н3ю]

Thank you for this course. Continue in the same way!

[@priyanshipatel7804]

indeed these videos are very comprehensive

[@kbillore28]

A function that takes const reference parameter can also be overloaded with a function which take reference parameter by passing const or non const parameter.

[@azadalishah2966]

Have you tried that? Const parameter function can be called by passing non-const variable as well. I believe const-parameter function is called when literal value is passed as argument

[@7thAttempt]

Excellent video! Thank you very much for sharing your C++ knowledge! :)

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[@pdd3]

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[@edlugoa]

Awesome video setting all the possible occurrences!!!

[@ghigopigo8317]

I just stumbled into this tutorial, i really like the style of it. My only worry is that it may not be up to date with modern c++ (?)

[@zili8317]

Your tutorial videos are really helpful! Thank you!

[@jarusll]

Awesome bro, well explained. These are really useful

[@isharthrastogi782]

exactly what i was looking for!

[@FRChang-g2o]

Thanks for sharing such a good tutorial!!

[@azadalishah2966]

At 5:55, non-const object d can call const function, does it mean that const function is called always by const or non-const object if no overloading non-const function?

[@s.d.gentry1354]

Very well done and informative.

[@davidbohadana8274]

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[@xty007]

amazing lessons, thank you so much!

[@alltheway99]

5:26 name is not a temporary, is in fact a data member

[@leelamanohar2001]

Please find the sample program for the exercise: #include using namespace std; class Dog{ public: void set_age(const int &) { cout

[@altafmahmud6095]

After following your lecture on lvalue and rvalue reference, I understood that "void setAge(const int& a)" will be invoked by following two types of invocations: 1. Passing an rvalue parameter: Dog d; d.setAge(10); 2. Passing a const int parameter: const int n = 10; Dog d; d.setAge(n); And "void setAge(int& a)" will be invoked by any lvalue parameter: Dog d; int n = 10; d.setAge(n); Now my question is with following code: int n = 10; const int& m = n; Why this works? In this context "d.setAge(n)" should have been ambiguous, isn't it?

[@4Seaofthoughts]

d.setAge(n) This calls setage(int &a),there is no ambiguity as n is lvalue.

[@maximus5415]

Great video, explained extremely well :]

[@elephiant8696]

Seriously good tutorial, thanks! :D

[@stshsngh1]

Great Work !!

[@ResZRyou]

Thanks for sharing the material.

[@bahalason]

Does it make sense to make a const function if the class doesn't have any private variables? Like a parser class for example. I could set every functions to const, but is there a need?

[@raviraja0559]

Very useful video...Thank you

[@omersagsoz9261]

do you have any tutorials, which contain the same topic but has pointers instead of references (e.g. const and pointers and functions)

[@williamchamberlain2263]

Nice summary

[@BrianVandrian]

Thanx I was trying to understand when to use and not use consts this weekend, so I made every conceivable function I could think of (return parameters and input parameters and I made this error 3:20 nd was curious about it). I'm going through templates and they are explaining them using const (Bleh...)

[@AmCanTech]

Thank you so much!!

[@aakupsp]

Why we can change pointer member variables inside a const function?

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[@Bopek]

genius, thank you

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I LOVE YOU

[@layssi]

Best explanation ever

[@slowthinker369]

Great tutorials. Subscribed.

[@priyanshipatel7804]

I want to ask,which one is better ide ,codeblocks or visual studio?

[@Kromush1995]

Got a question: when is good practice to return by const &? I know that by returning as const & you avoid calling the copy constructor on the object you return but also I've heard that it makes it thread unsafe, which is a little unclear to me why.

[@gunjan94_]

If we return a reference to an object and the caller keeps the reference too long - meaning the object may clear up or it gets changed before the caller uses it - this can lead to undefined behaviour in your program or it can work perfectly well as well in case its intentional - depends on how you have designed the program. Note that even if you return copy of the object, you still need to make things thread safe incase multiple threads are involved - lock on the object whose member is being accessed.

[@dmgkarthik]

can I invoke const functions from objects which are non constant ?

[@Colonel1954Dz]

You can cast them when invoking the value: static_cast(d).printDogName(); // This would print dummyconst

[@abdelaziz2788]

where is the lvalue and rvalue video???

[@foodlover3128]

How you get this good in c++. You know everything

[@riteshgupta5922]

Hi Bo, I tried to get answer when which function get call setAge(const int& a) or setAge(int& a). I tried by passing const and non const value in both case setAge(const int& a) get called. However for the same case if have these function as global then const version called for const value and non-const one for non-const value. Please help me know why only const version get called for class and how it works if function are global?

[@yogeshwalke1834]

If you pass rvalue or const value to the setAge function then it will call setAge (const int&a) . If you pass non const lvalue to SetAge function then it will call SetAge(int& a)

[@zahidkhankhan]

well explained. thanks for sharing. really appreciable..

[@badmuthahubbard]

Thank you for this. I have a question: Why bother passing a const reference as an argument? I mean, if you can't change it inside the function, why not just pass it by value?

[@Bing.W]

because it can be faster with const ref, where you save the copying.

[@spyrex3988]

for optimization

[@ligzer01]

keep up the good work!

[@bougpan88]

What is the ide that you use to make this c++ programming ? Thank you very much

[@nikolaikalashnikov4253]

He's using Netbeans IDE in this video.

[@bougpan88]

thank you very much

[@mandaputtra]

Thanks!

[@ragnarw.eliansson5299]

Very good!

[@mini_frank]

const referenced parameter will be invoked whent he caller is a const? regular reference parameter will be invoked when caller is a non-const? I am not sure, someone let me know if I am wrong.

[@mini_frank]

seems like const ref parameter will be invoked when setAge(5), else regular ref parameter function.

[@alditopalli9530]

what compiler do you use i have visual studio 2012?

[@madspace1234567]

Code Art this is NetBeans on Windows w/ MinGW.

[@BKJoe116]

Could there be a const non-member function, or is it a feature for member functions only

[@cobblin_gock]

any function can be const

[@gavinlangley8411]

+kayvan Mansoorshahi a const type qualifier is not valid on non member function the point is what is not going to change? all global variables?

[@mshri3286]

what is the IDE or editor being used ?

[@SAURAV1403406SAXENA]

age and name defaults to private right?

[@yonizerbib9934]

thanks!!

[@UltraAnalisis]

your voice sounds a bit difficult to understand, but you talk slow, that is good; thanks good video.

[@maciejkowalski3019]

Are you a native speaker? I come from Poland and I have no problems with his pronunciation.

[@saturn7_dev]

OMG - now I can see why I hate C++ so much. Its all so unnecessarily complex and confusing. I prefer to spend my brain energy on using simpler code that just works rather than on all these small details that can easily stuff you up - limiting how much actual useable code you write.

[@huyvole9724]

what relative beween double setAge and getName??

[@martinnieva8484]

What? Be more specific with your question.

[@williamchamberlain2263]

4:05 , 5:35,6:25,6:55

[@yonizerbib9934]

so, a class attribut is never const ?

[@jamesrockford2626]

very nice

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博主你好，你是中国人嘛，我最近也在学c++可不可以加个微信什么的，想向你学习一下😁

[@AkhileshPratapShahi]

const function..... please do repeat once more

[@sortysciaofiscia]

my mind: ............BLOOOWNN

[@vlad_serg]

sortysciaofiscia Your mind have not seen rValue-reference yet)

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Many people says wonders about this channel, but actually I find it quite confusing and not that helpful for a beginner! There are far better options around!

[@SecurityManager]

const int& a == int a ?

[@ldxyz-s1e]

3:12 6:33 7:03

[@delpacho]

where is the answer to the question???

[@RohitKumar-kr7ce]

d.setAge(static_cast(5)); will call void setAge(int& a) because 5 is casted into rvalue using && operator.

[@azadalishah2966]

5 is already rvalue, no need to cast

[@azadalishah2966]

setAge(40) will call setAge(const int& a) because literal 40 is rvalue and literal rvalue can’t be assigned to non-const lvalue reference.

[@ShivaPrasad-hm5lk]

9yrs 😯

[@ApoorvSaxena8]

very usfeull

[@DanHartwigMusic]

love your videos! but you name your dog dummy.... 🙁

[@BoQianTheProgrammer]

Netbeans.

[@jonnymcgrath4816]

Evil way to write codes

[@deborah_chrysoprase]

why give your dog such a mean name :(

[@virtuosisimo]

dogs are mean

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one of the conventions those old unix/bell lab people use. dummy variable. It's like _ in python : for _ in list

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Why is your name Lisa Jones Because I’m not a man

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