steel rune
Is there a reason why the creator of rust decided to make string concatenation work this way?
s3: String = s1 + &s2;
Like, why not simply make it work like this:
s3: String = &s1 + &s2;
// ofc this is invalid but it's a "what if"
Now all 3 strings are valid, the ownership isn't taken away from either s1 or s2. We just get a fresh String constructed from s1 and s2. And now symmetry is also restored back to the addition operator.
dense shell
I think this is from the idea that allocations should be explicit.
sick oracle
Ownership is taken away from s1
ops::Add takes ownership of the first operand and a reference to the second
dense shell
It takes ownership of both
steel rune
I think this is from the idea that allocations should be explicit.
well what if I wrote a function concat(&s1, &s2) wouldn't that violate that rule?
steel rune
yeah in rust it only takes ownership of the 1st String
neon aspen
If both sides are string slices then the implementation has no choice but to allocate a new String to store the result in. With the left hand side being an already allocated String it can just reuse that storage - say you chain multiple adds together, you wouldn't want to allocate a new String each time
dense shell
well what if I wrote a function `concat(&s1, &s2)` wouldn't that violate that ru...
It's not technically impossible, just unidiomatic. However, a function would be fine. This is about the basic operators allocating.
sick oracle
If you read the signature of Add, this is the only sensible way to do it
steel rune
If both sides are string slices then the implementation has no choice but to all...
yeah that is true, but if I wanted to reuse my 1st string's memory I'd write something like s1 += &s2 (assuming that that's valid in rust)
sick oracle
The way you gave also reuses the first string's memory
That's why ownership of s1 is taken
steel rune
If you read the signature of Add, this is the only sensible way to do it
ig my real question is, why is the signature of Add the way it is, why not take 2 references and produce a new thing
dense shell
Then you could never reuse the allocation
sick oracle
I think this is from the idea that allocations should be explicit.
Bc this
Rust makes you acknowledge new allocation
steel rune
hmm so for operatros all allocation has to be explicit
but it's fine if it's not explicit with functions that I write myself
sick oracle
It doesn't have to be that way, but that's the way it is by choice
dense shell
It's unidiomatic for the basic operators to allocate. There is no requirement by the language here, only style.
steel rune
so it's more of a rule of thumb?
dense shell
yes
steel rune
I see
well I'm not planning to change how it works lol
but at least now I see the reason behind it
thanks for the explanation guys
is there a ?solved command here or something similar to mark a topic as closed?
sick oracle
🤷
split wren
Is there a reason why the creator of rust decided to make string concatenation w...
I guess if I understand it is because if s1 where to be &s1 then it would be a reference then you know concatenation with a reference is not possible but now you might ask why not s1 + s2 . I think it is because s2 is being borrowed when concatenation occurs to create a new string so what basically happens under the hood is that s1 takes 1byte of space and s2 takes another seperate 1byte of space and now when you concate and assign to s3 then what happens is that it create a new space of 2byte and takes s1 by value which causes a move while s2 is borrowed and basically cloned under the hood which causes it to be reused again and again. To better understand this I have done some playing with your example and here are the errors and the code.
As you can see in the above image I able to reuse s3 as it gets borrowed which causes a clone under the hood while I cannot access s1 as it gets moved by value into the new space created.
Here is the error I get if I try to run this:
which shows that s1 gets moved by value while s3 gets cloned so that's why to fix this the compile clearly advices to use clone as this will make the reuse of s1 possible afterwards. I hope you got my point 🙂 . If you have further doubts feel free to ask I would be glad to help 🙂 .
Also Note I have used the word space for abbrevation what I actually mean by space is memory allocation or memory space allocation .
steel rune
off-topic but that's a sick bg for your code editor
steel rune
which shows that s1 gets moved by value while s3 gets cloned so that's why to fi...
everything is pretty clear to me, thanks for such a detailed explanation
split wren
off-topic but that's a sick bg for your code editor
Yes I am using catppuccin colorscheme for my code editor 🙂 .
steel rune
Yes I am using catppuccin colorscheme for my code editor 🙂 .
btw are you using nvim?
split wren
btw are you using nvim?
Yes you are right neovim 🙂 .
steel rune
cool cool
I use vscode, so that theme might not be available for me, but I'll look for alternatives that allow me to change the bg
split wren
I use vscode, so that theme might not be available for me, but I'll look for alt...
No it is available I would suggest taking a look here:
split wren
ty for the link
If you need any help regarding async-await, actix-web or any other rust stuff feel free to ping me here I would be glad to help 🙂 I hope you have a great day 🙂 .
steel rune
If you need any help regarding async-await, actix-web or any other rust stuff fe...
thanks a lot! btw do you have much experience with rocket? or other backend rust web frameworks?
split wren
thanks a lot! btw do you have much experience with rocket? or other backend rust...
Well to be honest I don't have much experience with rocket but I have a good amount of experience with actix-web so I would be able to help you with that if you don't mind 🙂
Also, one thing to note here with actix-web you will need to have some experience with async await in rust. Assuming you know it already then I would be really happy to help you out 🙂 .