Spyke

they used to call him the deref king back in college

108
mbpreply
slrpnk.net

Why would I want to be shown the concept of pointers by an eight year old?

3
wiesonreply
feddit.org

Nah, she's 5 or younger. She lied about being 6 (school age) to get adopted. It's a very wholesome story (if you disregard the war, political intrigue and terrorism).

15
sh.itjust.works

And the fact that Anya's best friend is trying to break up Anya's parents because she has a crush on the dad

5
Susagareply
sh.itjust.works

I think int*** is meant to be pointing at int**, but the image is just unclear about where everything is in perspective.

83
dohpaz42reply
lemmy.world

Pretty sure the image is clear:

int*** -> int*
int** -> int
Int* -> int

Clarity doesn’t mean correct. But that’s probably why it’s posted here. 🤷‍♂️

28

int** is inside a TV, and persumably int* must be inside another TV(even though uts not edited in). The image perespective is showing one thing inside the other, inside the other. So when when int*** points the TV it reference int**, which reference int* which reference int. Its just edited very bad

9
Susagareply
sh.itjust.works

RT*** isn't pointing at RT*, he's pointing at the TV showing RT**. The fact you think otherwise is what makes the image unclear. I'm not sure why you insist on them being wrong.

8

But that doesn't hold up, because RT** isn't pointing at a TV containing RT* only RT*** is pointing at an TV containing RT** RT* and RT

0
Monumentreply
piefed.world

It’s to check to see if commenters know how to escape the symbol. Congratulations! You passed!

Source: I made it up.

4

I mean, that's pretty much what happens to me every time I try to use pointers, so the meme checks out.

15

That's not the end of the chain either, right?

Because : int -> &int -> &&int

Or can you not use the address operator like that? It also might be int& &, I failed cs2200 on this exact type of technicality

3
lemmy.zip

Why should the left one in the rectangle be int**? It doesn't make sense to me, they are both clearly just int*

What am i missing?

8

I they're supposed to be pointing at each other but the edit didn't really work because his arm is pointing too far away

9
lemmy.zip

So, googling it, the general premise is you should use smart pointers instead to avoid crashes. Got it.

8
lemmy.zip

Unlike many other programming languages, which are often picked up on the go from tutorials found on the Internet, few are able to quickly pick up C++ without studying a well-written C++ book. It is way too big and complex for doing this. In fact, it is so big and complex, that there are very many very bad C++ books out there. And we are not talking about bad style, but things like sporting glaringly obvious factual errors and promoting abysmally bad programming styles.

https://stackoverflow.com/questions/388242/the-definitive-c-book-guide-and-list

6

Considering that most of the "answers" I've found on StackOverflow were complete dogshit, I'm wary of this reading list

6
CanadaPlusreply
lemmy.sdf.org

They all have footguns that cause different crashes.

If you want to do explicit memory access without inevitable safety problems, you need Rust. That's the whole hype with Rust.

4

So you really should implement it in your compiler so you don't contravene it

2

Sure, that may be (it's definitely not in userspace). But don't forget it works by crashing your program.

2
lemmy.zip

Real talk: is there any practical use-case for T*** of any pointee type?

7
Technusreply
lemmy.zip

Ah right, so that would be a 3D array.

  • T* is a single row of T
  • T** is a list of rows
  • T*** is a list of "layers" in the third dimension

This would be incredibly hazardous to pass around as a bare pointer with no context, though. I'd expect to see this in a struct that, at minimum, also includes fields for the size of each dimension.

12
fedia.io

In the C programming language. Or do you mean which C project specifically? Because as Technus surmises in their response, it's usually a better idea to set up aliases (typedefs or heck, even #defines) so that you're offloading some of the mental strain keeping track of the layers, and that's likely to be what happens in production code.

But the underlying data type is still T***.

3
lemmy.world

The & operator references the value.

int i;
int* p = &i;

In C++, the & at the function argument makes it a reference type (safe pointer).

void someFunction(int& refVal) {
    [...]
}
6
Flames5123reply
sh.itjust.works

As someone who likes working with higher level languages, I never understood the pass by reference or even referencing different pointers. It never stuck out to me as useful in what I want software to do. It’s too close to hardware.

1
lime!reply
feddit.nu

if you're working with higher level languages you pass-by-reference all the time. give a list to a function to modify it? that's by reference. giving an event handler function to a framework? that's by reference. setting a property on an object? that's usually by reference.

10
sh.itjust.works

the list is the helpful part to understanding it.

it would be terrible if, with bar being a list and foo being a member of the list

 if foo in bar: return true

modified the list. So yeah, you want to look at the list not edit the list, it's a pointer.

0

other way round surely? if you want to modify the original object, use a pointer. if you don't, use a copy.

4

Your example doesn't make sense to me. Why would you modify the entire list by checking if something is in it? Also, you can totally edit the list via a pointer, that's how you're supposed to edit the list if you want any performance. Otherwise you'd be copying the list on every modification, which is terribly inefficient

2
Sylvartasreply
lemmy.dbzer0.com

A pointer to the list would allow you to modify whatever's at that pointer's address though. If you want to look at the list and not edit it you pass by const reference 99% of the time (or you pass a copy) and if your language doesn't have that I don't like it.

1
lemmy.world

I still don't get the point of pointers.

I want my language to pass by reference. I give a variable to a function and the variable in the function scope should be a reference to the same place in memory as the original variable.

How can pointers help me here? What value does it provide? Genuine question.

2

I want my language to pass by reference. I give a variable to a function and the variable in the function scope should be a reference to the same place in memory as the original variable.

I'm not even a C++ wizard or anything (though it's my most advanced language) so I'm not gonna argue that is good or bad, that sounds fine to me for a wide range of applications already.

But the way is see it, pointers kinda allow you to use "raw memory" which is an actual thing that's gonna be handled by the program one way or another, and it's a way to relatively refer to memory for example. As some guy on stackoverflow put it "That guy at the end for the bar" vs "Bob" can be very useful. Especially when using data structures you don't know the size of at compile time.

2
Sylvartasreply
lemmy.dbzer0.com

Most of the time you pass by reference for more outputs, or by const ref to avoid copying a big-ass data structure (which is not always straightforward, with structures smaller than a pointer, which are pretty big in 64 bits architecture, you lose more to the ref overhead than to the copy IIRC)

10

Another reason I commonly see: to change the structure / "main pointer" to a data structure (esp during freeing and cleanup).

4

Reference values are quite useful, such as:

double valOut;
if (parseDouble(valOut) == 0) { //Argument of parseDouble is ref type, no & needed for input, no exceptions needed for error handling
    [...] //No error, code executed normally
} else {
    [...] //Erroreus input
}
1

*x = dereference or "point to". Treats the variable x as containing a pointer value. Evaluates to a variable existing at the address in x.

&x = reference or "get address of". Evaluates to the address of x.

They're complimentary operators, so *(&x) cancels out and is equvalent to just x.

4

No, you need to learn a lot more. Other programming concepts, programming paradigms, algorithms, and many more.

0

The placement of the labels is a bit sloppy but I think it tracks. The character in the middle (int*) is pointing at int, then the one on the left (int**) is pointing at the middle one (int*), etc

What I want to know: what is that shirt and where do I get it?

3
addiereply
feddit.uk

He dereferenced a pointer to the 1970s and retrieved the shirt that way.

2

It’s what makes mages turn those squiggly lines on paper into fireballs.

Not clerics though, they’re different.

3