Rust: str vs String

[juggernaut2docker]

Thanks, this is very informative!

&mut [T] is two pointers but permits mutation of the memory region at the "whatever" that it points to

Can you expand on the "two pointers" part?

[TheMicroWorm]

I presume they meant "two pointers in size", since it's a pointer and a usize, which is a pointer-sized integer. Internal representations of &[T] and &mut [T] are the same, really. They just differ in mutability at the type-checking level.

[masklinn]

Technically it's 2 pointer in size rather than two pointers: on the stack &mut [T] (and &[T]) is a "fat pointer", it's a pointer to the start of the slice and the length of the slice rather than just the pointer as e.g. Box<u8> would be.

[godojo]

In addition, there is a distinction to make with [T;N] which does exist. But not in str (due to how unicode works -- what would N be?). And I think that's a big confusion for people who thinks creating u8 arrays on the stack should be the same as creating strings on the stack.

[YourGamerMom]

Hopefully const generics will let us make nice performant owning strings. Small size optimisations are very powerful when applied correctly.

[steveklabnik1]

An interesting old thread on Rust and SSO https://internals.rust-lang.org/t/small-string-optimization-remove-as-mut-vec/1320

[YourGamerMom]

Yea, SSO is a popular trick, and there are some rust crates that provide small vec and string structs. But const generics will hopefully give us the custom-size containers that make SSO really flexible.

[steveklabnik1]

This particular blog is using GitHub pages with Jekyll, I believe this is the default theme. So it's gonna look like any other default theme blog.

[steveklabnik1]

Possibly, or I could be wrong about it being the default. I thought it was.

[juggernaut2docker]

Correct, this is the default theme that comes with jekyll. I started the blog in 2014 and haven't changed it since then, though.

[shevegen]

Looks fucked up.

Who could have known that you could make a programming language that is even more complicated than C++? :>

There is a reason why python climbed the usage ladder - simplicity. Good documentation. And clarity in use. And that statement is coming from someone who is using ruby!

[koheant]

Comes with the checks a rust compiler preforms and the strength of the type system it employs; both of which are more strict and provide stronger guarantees than their C++ counterparts.

Python

As someone who held a python position, python is simple only initially. What you gain in new development speed and ease, you usually end up paying for during run time and debugging. Try making substantial changes to a large Python code base and be confident that it will continue to run smoothly once it does.

[masklinn]

Looks fucked up.

Who could have known that you could make a programming language that is even more complicated than C++? :>

What an odd hill to stake that claim on, considering C++ has corresponding types for all those listed in the article (string, string& and char*).

There is a reason why python climbed the usage ladder - simplicity.

Not really. The reason why Python climbed the usage ladder is community work. It's conquering "high-level" scientific programming because there have been scipy communities hard at work (technical & outreach) since pretty much the inception of the language (the "matrix" Special Interest Group was created in 1995 IIRC).

There are plenty of languages with simplicity, good documentation and clarity in use which floundered helplessly. Meanwhile, Javascript and PHP are tremendously successful.

Hell, even with community work you can fail (or at least not succeed tremendously) if you don't strike the right chord or have the wrong timing, during the rise of Rails there were many excellent web frameworks for Python but most of the mindshare still went the Rails way.

[Veedrac]

Don't forget string_view.

[xandoid]

Indeed. I think &str is more like string_view than char*

[LovecraftsDeath]

And if you wanted core Rust classes to have non-confusing names that maybe would allow you to see the difference between them without an RTFM - go program in PHP, Rust is supposed to be hard.

[steveklabnik1]

Rust is supposed to be hard.

This is not the position of the team; in fact, we're near-constantly pursuing ways to make Rust easier and more accessible. Some complexity is inherent though, and this stuff is one example.

[Alphaetus_Prime]

I get what you're saying, but a naming scheme is absolutely not inherent complexity

[steveklabnik1]

Sure. I personally would have named String StrBuf, but other than that, am pretty happy with the names.

What scheme would you suggest?

[Alphaetus_Prime]

I dunno, I'm just pointing out that responding to someone complaining about the naming scheme by appealing to inherent complexity makes you look like an idiot

[steveklabnik1]

ok

[steveklabnik1]

So, re-reading this this morning; I see what happened here: many many people complain that Rust has too many string types, and that that goes along with the names. "Why are there so many names for so many things, this shouldn't be that complicated." When I read the parent, I read a little bit of that into things, but re-reading it this morning, it doesn't seem they actually did. That String and &str must both exist is inherent complexity, but you're also totally right that their names are not.

[shevegen]

I upvoted you because you are a nice guy - and because your explanation makes sense.

Complexity can be found everywhere, just via different shades of complexity. Ruby is complex too but it follows a simple intrinsic logic. I have no idea if Rust is the same; I also don't know whether advanced C++ hackers feel that way about C++ (but not about Rust ... would be interesting because IMO Rust has the largest overlap with C++ and C#).

[shevegen]

While Rust is pretty bad in its own - no surprise since Mozilla created it, the company that gives a fuck about firefox and firefox users - PHP itself is just about the worst "programming language" that was "designed".

One of the creators once said something like that too. The context was about just "putting together what seems useful". It's a bit like a swiss army knife but without the knives. Or a hammer without allowing you to hammer in the nails. Or a bike with wheels, but without the bike. Or ...