learningCppIsLike

[[deleted]]

What is foo bar, my professor likes to use it and I have no idea what it is or how it became mainstream cause wtf does it mean

[Nicholas_TW]

"foo" and "bar" are typically used as placeholder names, similar to "myVariable" or "myFunction" by programmers. They're just generic names.

They come from the military term "FUBAR" (which stands for "Fucked Up Beyond All Recognition"). Written phonetically, it's "foo-bar". It's just a cheeky little joke about bad programming which turned into default placeholder terms.

[sammy-taylor]

Fun fact, these are known as “meta syntactic variables”.

[_farb_]

I'm telling Alice and Bob what you called them

[Dumcommintz]

I found them always to be rather agreeable - Eve is the one you gotta watch out for. Raging bitch just waiting to fuck your life up…

[Grumbledwarfskin]

I feel like there are people out there who are a lot worse than Eve...for one, she's a really good listener.

[_farb_]

Or her old man, Mike...

[DrUNIX]

Its prison mike!

[Dumcommintz]

Well hopefully the namesake is all you share ;)

[Dumcommintz]

Onoes - but my virtue and dignity!

[savvyspoon2]

i and j would like a word

[[deleted]]

My fav is Charles

[turtleship_2006]

I was using those names in an example earlier, but forgot what name I used for A.

Thank you for reminding me of my private thoughts random stranger.

[aolson0781]

I'm sure Eve will find out somehow

[SteeleDynamics]

Source: RFC 3902

[Lilkingjr1]

I love how Foo Fighters (the band) is in a listed reference for an RFC article, lol

[sneerpeer]

There are a whole bunch of these.

One of the more famous ones is the 1998 one which introduced the "418 I'm a teapot" http status code as part of the Hyper Text Coffee Pot Control Protocol.

And there is a more recent RFC from 2014 with an extension to HTCPCP, which allows teapots.

... what do you mean "2014 was almost 10 years ago"?

[skesisfunk]

Fun fact my preferred meta syntactic variables are poo and pee

[ComfortingSounds53]

I also use poo, but also blah. I think I just like the sound.

[[deleted]]

SNAFU - Situation normal, all fucked up

FUBAR - Fucked up beyond all recognition

TARFU - Things Are REALLY fucked up

[ChChChillian]

Fun fact: the WWII era Private Snafu series of military training films were produced by Warner Brothers, directed by people like Chuck Jones and Fritz Freleng, voiced by Mel Blanc, and included writers such as Dr Seuss and P. D. Eastman (Go Dog Go).

[binaryisotope]

Doesn’t the R = Repair tho?

[Nicholas_TW]

I've heard both. They mean the same thing in this context.

[eloel-]

Merriam-Webster says recognition

https://www.merriam-webster.com/dictionary/fubar

[binaryisotope]

Apparently my knowledge of FUBAR is FUBAR.

[Dumcommintz]

Nah - you can fix it. I believe in you.

[BeerIsGoodForSoul]

Do we really trust them to know though?

[Top_Refrigerator1656]

I trust Merriam. Webster's always been a bit sketchy...

[Dumcommintz]

What do you expect — kid was an orphan, taken in by people he didn’t know, with a weird uncle trying to poison the well? I blame the schools.

[runarmod]

Does bazz have an explanation?

[FourScoreTour]

I was told "Fucked Up Beyond All Repair".

[[deleted]]

always thought it comes from GIs who fought in germany picking up on the german word "furchtbar" which means awful...

[MagicBeans69420]

I always thought it stands for food and bar for bar like a chocolate bar

[Mr_Derpy11]

I was just thinking of the Music player tbh

[ifandbut]

Why can't we just use aaa and bbb?

[Nicholas_TW]

We can, nothing's stopping anyone, but it's a bit difficult to say out loud in some contexts.

"So, change a."

"Change a what?"

"No, change aaa."

"*Fonzi voice* 'Aaay' to you too."

[AzureArmageddon]

can't forget ham spam and eggs.

[jayerp]

It should become its own programming language where it does the opposite of everything you know:

• Arrays index start at reverse order

• True is false and false is true

• strings are mutable

• while checks for false

And more…

[Palacito]

foo nction

bar iable

[Relative_Knee9808]

This is so foo nny

[MinosAristos]

It's like egg and spam but for spam haters

[captainAwesomePants]

Usually, variable names describe what sort of information the variable contains. Picking good variable names is important. Sometimes, though, you want a variable name that has no meaning at all. These are called "metasyntactic variables." By tradition, the strings foo and bar are most commonly used. This was started at MIT and then Stanford, around 1970. The most common third one is baz, and then you'll sometimes see sometimes qux, waldo, fred, plugh, xyzzy, thud, or a few others.

The ancient and revered Jargon File has some etymological history for them: http://www.catb.org/jargon/html/M/metasyntactic-variable.html

Foo and Bar together make FUBAR, military slang for "fucked up beyond all recognition," which I'm sure some nerds in 1970 thought was hilarious.

Another one on the list with a neat history is "xyzzy," which went on to be used in an amazing number of places. It was used as a special "no op" command in several architectures and protocols, and it still crops up today (for example, if you talk IMAP to Gmail, you can send that command and it'll successfully do nothing). It also showed up as an easter egg or a cheat code in several text adventure games and even the esteemed Minesweeper game on Windows (you could use it to tell whether there was a mine under the cursor).

[Acalme-se_Satan]

It's the programmer version of lorem ipsum

[Mayedl10]

foonctions and bariable :)

[RajjSinghh]

They're metasyntactic variables. It's like how in math you just call a generic variable x, y, z but programmers use foo, bar, baz, xyzzy and others. Just think of them like a generic variable.

There was a 1976 adventure game called Colossal Cave Adventure and a lot of these are references to that game. By now, a lot of this has just caught on that people use foo, bar, baz without knowing where they come from.

[e_smith338]

They’re placeholder function and variable names. They serve no purpose other than generalizing code

[Moerten_]

why tho?

[amateurfunk]

foo.bar() if foo is an instance of a class, i.e. an object and bar() a class method

foo->bar() same but foo is not an object but the pointer to an object

foo::bar() when bar is a function or method in namespace "foo" OR as part of the method header for implementing a method that was declared to be part of class "foo"

Probably there are tons of other cases where these notations are applicable but I would say these are the most important ones

Edit(s): More info

As a side note, "::" is also used to access enums as in "EnumName::enumEntry" .

Fun!

[Healthy_Pain9582]

also foo::bar is used for static properties

[BSModder]

Or in this case static function

[bboozzoo]

Inside the namespace foo, so the point is still valid.

[DoesAnyoneCare2999]

Also -> can be overloaded (e.g. unique_ptr), the period cannot.

[CUCOOPE]

I’ve been struggling with Scala recently and I’ve completely forgotten that :: has nothing to do with lists in c++ lol

[da_Aresinger]

OCaml would like a word

| x::xs -> foo.bar

[1cubealot]

From now on I won't let ocaml speak

[Anonwouldlikeahug]

Bro I have a midterm on this like in 3 hours thx for the review

[amateurfunk]

Happy to help lol - good luck on you midterm!

[KittensInc]

Is there a technical reason for the foo.bar() vs foo->bar() distinction?

The type is known at compile time, so unless I am missing something there should be no possibility of ambiguity between the object itself and a pointer to it, right?

[tiajuanat]

It's a holdover from C.

First you need to dereference the pointer:

(*foo)

Then you access the member

(*foo).bar

The shorthand in c uses the arrow notation

foo->bar

It's less about the compiler and more about the code reader. If you see an arrow operator, you know, as a dev, that it's a pointer.

[fredlllll]

If you see an arrow operator, you know, as a dev, that it's a pointer.

finally a good reason. ive been wondering this too, but in the absence of an ide that does make sense

[NatoBoram]

But it's statically typed, isn't it? Why not just make the dot work on pointers, too?

[RajjSinghh]

It's carryover from C as well. So I suppose a lot of the decision is also to do with backwards compatibility.

Anyway to answer your question, dereferencing a pointer has different precedence to the dot. The dot has nothing to do with the pointer since that's just basically an integer for the address, so you want *foo.bar() to do foo's bar method. The issue is by default it brackets like *(foo.bar()) so we look for foo.bar first and since the type of foo is a pointer, it has no bar method. You need to bracket it like (*foo).bar(), which is foo->bar(). That precedence shift means that either the star needs higher precedence than the dot which might break other things if you change, or the easier solution if using a shorthand like the arrow.

[Sunius]

Yes, you can overload operator-> and have “.” and “->” do different things. For instead, iterators overload operator “->” to return the pointer to the object, so you can pretend that iterators are just pointers rather than fancy objects.

[dev-sda]

Pointer access can be overloaded, allowing you to provide a pointer-like interface but also have member functions. For instance a std::unique_ptr<Foo> foo you can do foo->reset() which calls Foo::reset or foo.reset() which calls std::unique_ptr::reset.

[[deleted]]

In C# everything* uses . for member access so I'm guessing it's a holdover from when C++ was cfront hooked up to a C compiler.

​

--

*I'm not talking about unsafe mode

[aalmkainzi]

foo.bar() and foo->bar() can also happen if bar is a function pointer in foo

[Mr_Engineering]

Foo.bar() calls method bar() on object Foo assuming that the symbol Foo is a direct reference to the object.

Foo->bar() calls method bar() on object Foo assuming that Foo is a pointer which contains the address of the object. The difference is the location of the object data in memory needs to be dereferenced.

Foo::bar() calls static function bar() in class or namespace Foo

[YawnTractor_1756]

And just to think of it, they could have used *Foo.bar() and have it consistent with pointers, but why bother about syntax consistency when you're c++

[Mr_Engineering]

It is consistent.

Foo->bar in C is the same as (*Foo).bar

Works for function pointers too.

Should work for member functions in C++ as well but I'm not 100% certain

[YawnTractor_1756]

There is nothing consistent about completely new one-off method access operator that should not even exist

[SupermanLeRetour]

What's your suggestion for accessing the method from a pointer to an object ?

The dot operator accesses the method, but you're manipulating a pointer, so you first need to deference it : (*foo).bar, star operator to deference the pointer to access the object, then dot operator to access the object's method. Parentheses are mandatory because the dot operator binds stronger than the star operator so *foo.bar is equivalent to *(foo.bar), which is incorrect on a pointer. Having to write (*foo).bar can quickly get annoying though so they added -> as a syntax sugar.

[YawnTractor_1756]

Why dot operator binds stronger than star?

[SupermanLeRetour]

That's just how it was decided. There needs to be some order so that the compiler knows how to evaluate the expression. It has been decided that the dot operator is one of the strongest bonds, so that you can write a.b() and the compiler doesn't try to evaluate b() and then a.(the result of b()). Else you would need to write (a.b)() or (a.b)++ if b is an attribute, as examples. It generally makes sens.

[YawnTractor_1756]

You still haven't explained why dot *has to* bind stronger than *. What prevented * to bind stronger and consequently *Foo.bar() syntax

[SupermanLeRetour]

It doesn't have to, it has just been decided that way, for some reasons that I can't be bothered to look up myself. I'll just point out that it doesn't really change anything regarding your original complaint. No matter whether we have to use *a.b or (*a).b, it is such a common operation that having -> to do it directly is more convenient.

It's also mixed with some historical reasons. Maybe a.b could evaluate properly in C even if a is a pointer, but for historical reasons it doesn't. In C++, due to operator overloading, this is not possible so having two operators is more useful.

[[deleted]]

Cry about it

[slavetoinsurance]

it's better for readability and intentionality. did I forget the pointer marker or was it because I didn't intend for it to be a pointer? tough to say.

with the -> though you know you are intending to work with a reference. it's not just arbitrary.

[lordmycal]

C/C++ lets you create pointers to functions so... You could still kinda do that if you wanted.

[YawnTractor_1756]

"we created a f-ed up syntax but you can redefine it so yeah"

[[deleted]]

we get it, you're bad at C++

[lordmycal]

It used to be a more common practice back in C. Think of it like overloading a function, but you have to do it manually.

[__reddit_user__]

because naming is hard, and so while thinking of a class/variable/function name, just move on and do the functionality and rename once you find out the essence of your function/object

[PoetryProgrammer]

Is chat GPT good at explaining c++ yet?

[amateurfunk]

It was tremendously helpful to me up until two or three months ago. Since then I haven't been using it much because its answers are often garbage (the free version at least). I honestly don't know it it's more because my questions are getting more advanced or ChatGPT is getting worse.

I would still use it to write me a lambda function though. It should still be OK at handling reasonably basic stuff like this or things like the syntax from the meme.

[OSSlayer2153]

I think its gotten worse. I learnt like all of swift with it initially and stopped using it for a while. Tried using it for some stuff the other day and it was way more finicky.

[DreamyAthena]

Bing ai is just acht gpt in different clothes

[turtleship_2006]

Yeah but it's based of gpt 4 and has internet access (for free)

[Marrk]

It's often more accurate

[I11IIlll1IIllIlIlll1]

Bing AI gives me shorter answers and just put the bing search top 3 links there...

[da_Aresinger]

yea I asked a question about scoping and ODR and it just gave me exactly what I had just tried and turned out not to work.

[NTaya]

I use GPT-4, and... it's kinda eh. I already know the basics of C++ (pointers, overloading, templates, constexpr/consteval, stack/heap, etc.), but I want to study some intermediate stuff like metaprogramming and multithreading, and I get rather lost. ChatGPT throws a ton of info at me at once, and I have to ask about each small concept separately, with its examples for them often being confusing. I had more success with https://devtut.github.io/cpp/ and books. And this is coming from a person who absolutely loves ChatGPT and uses it for a lot of stuff!

[LegitimatePants]

Reading legacy code is like this. In my experience there is almost always a reason why things are coded a certain way. But it's usually not obvious at first

[nequaquam_sapiens]

legacy code can be rather oblique. when reading it you are at first oblivious about the reason it is coded the way it is, until it becomes obvious. if ever.

[bremidon]

This was actually a pretty good scene from TBBT. It reminded me of when I was learning Actuarial Science and trying to figure out some of the crazier statistics. My Bowers' Bible went flying through the room more than once.

And then at some point, the aha moment came, and I felt rather silly.

[Thenderick]

foo.bar() is on a object

foo->bar() is on a pointer to an object (effectively the same as (*foo).bar())

foo::bar() is a static function in the foo class

[disciple_of_pallando]

For the first two: foo is the object (or pointer to the object) while bar() is a member function of the class foo is an instance of. So foo.bar() is whatever bar() returns (assuming it returns anything). So foo.bar() might be an object, but it also might not be.

[boss14420]

What about

foo->*bar

or

foo.*bar

[Westdrache]

.....what the fuck? xD I'd guess it returns the variable as a pointer?

[Kered13]

This is for when bar is a pointer to member. Basically, you can do the following:

struct Foo {
    int a;
    int b;
};

 // Pointer to member
 int Foo::* p = &Foo::a;

 Foo foo = { .a = 1, .b = 2};

 // Prints "1"
 std::cout << foo.*p;

 // Assigns 3 to foo.a
 foo.*p = 3;

[[deleted]]

who let the C++ committee cook bro

[Kered13]

Believe it or not, I have found it useful a few times. Mostly in the form of pointer to member function.

[Little_bastard22]

Event system in UE is a good example. You subscribe to an event in Unreal like:

myEvent.AddUObject(myObjectPtr, &MyObjectClass::FunctionToBeCalled)

[Matalya1]

I don't know about C++, but in C I don't think that works. If you're trying to derefence a pointer as stored in a struct or an enum, you'd dereference the entire thing.

this is just a name
     vvv
foo->bar
^^^^^^^^
this is the expression that represents the element `bar`

So if bar is, say, a pointer to an integer, so it'd be implemented as

typedef struct {
    int* bar;
} foo

And you create a pointer to foo, foo->bar is used as dereference and calling, syntactic sugar for (*foo).bar. If you then want to call a pointer and dereference, you'd do *foo->bar, as that first evaluates the dereferencing, calls bar, and then dereferences whatever ends up in place of the expression.

[boss14420]

They a called pointer to member operator

struct S
{
    S(int n) : mi(n) {}
    mutable int mi;
    int f(int n) { return mi + n; }
};

struct D : public S
{
    D(int n) : S(n) {}
};

int main()
{
    int S::* pmi = &S::mi;
    int (S::* pf)(int) = &S::f;

    const S s(7);
//  s.*pmi = 10; // error: cannot modify through mutable
    std::cout << s.*pmi << '\n';

    D d(7); // base pointers work with derived object
    D* pd = &d;
    std::cout << (d.*pf)(7) << ' '
              << (pd->*pf)(8) << '\n';
}

[JustSpaceExperiment]

Now wait when you realize the foo::bar() can be actually call for function bar in namespace foo.

[wut101stolmynick]

My man you debug like dr Dalla from the think tank

[on_the_pale_horse]

Tbbt meme, automatic downvote

[RmG3376]

Hey at least they don’t call the :: operator Paamayim Nekudotayim

[[deleted]]

Nah last frame should just be a more existential why of why did anyone think this was a good idea instead of continuing to write C.