Concatenating strings in a GC language is easy, you just "+" them together, the cleanup will happen eventually. Concatenating in low-level languages means you have to think about the memory allocation(s) taking place, and the format("{}{}") is a lot more powerful for anything more than just adding two strings. What if you want to prepend "https://"? In GC languages, this might be an extra string being allocated and discarded, in Rust, it's a constant hard-coded into the binary. It just happens that the language has attracted a lot of people who are used to higher-level abstractions due to it's relatively pleasant syntax, type system and abstractions, ecosystem and perfomance.
Another example is span, while C#'s Span and Microsoft's gsl::span do bounds checking, ISO C++17 span naturally leaves it to the developer's responsibility.
No, the idea was to make a simple one-to-one wrapper for the "char, char" pairs programmers were already using all over the place, nothing more.
For anything else, it isn't worth the productivity drop of automated memory management (regardless in what form) coupled with value types.
Meanwhile in the real world: "I find myself hanging for long periods of time on borrow checker errors. One of the errors has stopped my progress dead for a week now, I swear it worked a week ago and then Rust decided that a borrow I was doing was no good." [2]
I do recall the steep learning curve and the frustrations with the borrow checker, but I haven’t had it impede me at all in probably two years now and I’m writing Rust most of the day every day.
Also, most of the knowledge I gained by learning to work with it is general knowledge that made me a better programmer, not specific knowledge of how to “work around” the borrow checker.
When people do things you don't understand, don't just say that they're just doing it because it's fashionable. Sure, they might be — or they have their own reasons.
I use Rust in a couple of places outside of its original "systems programming" niche, where, yeah, I don't really need to track every allocation, I don't care about GC pauses, I don't need to ship one single binary, and the overhead of a runtime wouldn't bother me. Things like Web servers for side projects, or small scripts to do a task I need to automate.
However, I found that:
• The effort it took to bring Rust out of its niche, and the time it took to learn the domain-specific libraries for my use cases (Rocket for Web stuff; duct for shell script stuff) was less than I thought;
• The amount of knowledge I needed to retain to use a programming language effectively — the components of its standard library, common third-party helper libraries, how to navigate the documentation, how to fix mistakes, how to avoid traps and pitfalls, how to structure your program, how to handle differences between language versions — was much larger than I thought!
So I stick with Rust for non-systems tasks because the benefits outweigh the detriments for me.
(Granted, I was only able to do this because I already knew my way around the language and the borrow checker; if you already know, say, Python, you can make this exact same argument in reverse. But then you need to know how to wield Python for low-level programming as well as high-level programming.)
I read an article a few years ago called Java for Everything[1] (which was discussed here on HN[2]) that makes the same point, only with Java. If I had to pick an "everything language", I don't think it would be 2014-era Java, but the article did sell me on the benefits of having an "everything language" in the first place, and I feel the same benefits apply here with Rust.
[1]: https://www.teamten.com/lawrence/writings/java-for-everythin... [2]: https://news.ycombinator.com/item?id=8677556
However we are slowly moving back into multi-processes as way to avoid in-process security exploits and improve overall application stability.
In these kind of scenarios, there is little that Rust type system can help regarding races in IPC.
1. Functions which convert a number to a string, where the target string is a byte buffer passed into the function as a pointer argument. This allows C developers to pass pointers to statically-sized arrays of bytes, which leads to buffer overflows. (Inb4 someone shows up with "but that's the programmer's fault for not using an array that's big enough".) Example: strcpy.
2. Functions which return pointers to static storage, which makes them thread-unsafe, and even in single-threaded cases is error-prone, when you call one such function multiple times in succession (aliasing). Example: gmtime.
Both cases are very prominent in the standard library.
If instead functions allocated memory dynamically, then they would avoid buffer overflow, because size would be handled exclusively within those functions, allocating as much memory as is needed, no more, no less; instead of forcing the programmer to worry about the size at every call-site. They could also be easily made thread-safe and less error-prone (eliminating aliasing), provided that the allocator is thread-safe.
Another issue with the first case is that it leads to uninitialised variables. Often a pattern of "bool NumToString(int n, char* dst, int size);" is employed instead of "Optional<std::string> NumToString(int n);". This invites the possibility of using "dst" without checking the return value, which says if the conversion succeeded. In this case dst is most likely uninitialised, and definitely incorrect. An "Optional<std::string>" solves both issues.
The C stdlib string API is rubbish of course (along with most other C stdlib APIs). But at least it's quite simple in C to ignore the stdlib (and use better 3rd-party-libs instead) without loosing important language features.
Rust helps lift than mental load because if you're in safe rust then you knows the compiler will catch these problems for you. It also makes quite explicit when you're on the stack or heap.
I also love the explicit mut keyword makes functions very easy to reason about. In Go I find pointers being used for three purposes, to act as a reference, to act as an optional (nullable) or to act as a mutable parameter, and it's impossible to tell which by looking at the function signature and I can't tell you how many bugs that's caused in our codebase
The bicycle you pick depends on the problem you're trying to solve. You can divide up all programming languages into two categories:
1. Those that allow you to state your problem in terms of ideas. You write your code, the compiler or interpreter does some optimisations, and the end result runs fast enough for your use case.
2. Those that allow you to state your problem in terms of machine instructions. You demand a certain level of performance, or want every memory allocation to be explicit. The compiler or interpreter still does some optimisations, but instead of inserting more instructions implicitly if it has to, you'd rather your program straight-up fail to build.
The choices made by a language's designers will make it seem unnecessarily complicated if you're looking at a (2) language when you have a (1) problem, and will seem like it's making too many assumptions for you if you're looking at a (1) language with a (2) problem.
For example, let's go back to string concatenation, which, as you saw in Rust, looks like this:
format!("{}{}", x, y)
x + y
concat(x, y)
But a String in Rust, under the hood, contains a pointer to a heap-allocated buffer. And getting one of those requires a memory allocation, and Rust makes those explicit. So the method of concatenating two strings you choose depends on what machine instructions you pick:
• If you don't really care, or if you need a new heap-allocated buffer, then `format!("{}{}", x, y)` will give you what you want.
• If `x` is already a heap-allocated String, and you know for a fact that you aren't going to need to use it again, then you can re-use the existing buffer with simply `x + y` (or something like `x.push_str(y)`).
• If `y` is a heap-allocated String but `x` isn't, you can re-use that existing buffer with `y.insert_str(0, x)` (but this requires it to copy the bytes in the buffer to make room for the string you're inserting).
• If neither is a heap-allocated String, and you don't want to allocate any more memory, you'll have to skip concatenation altogether and do something else (for example, if you're just writing the concatenated string somewhere, and don't need a buffer to put it in, then you can do `write!(somewhere, "{}{}", x, y)` which won't allocate).
> Surely the computer should be doing the heavy lifting?
I find that the Rust compiler does an excellent job of doing the heavy lifting for me: I don't have to worry about iterator invalidation or use-after-free, surprise memory allocations or numeric type conversions, or unexpected performance drops when I make a small change. But this is all because I'm expecting a type (2) language, rather than a type (1) language.
It's the last part I'd like to focus on, because you may have read the above list and thought "a compiler could choose the appropriate optimisation for me!". And, well, it probably could! After all, if the only difference between the first option `format!("{}{}", x, y)` and the second option `x + y` is whether the string `x` gets used after concatenation or not, a compiler could certainly check whether this happens and optimise out the allocation if necessary.
But then you need to worry about keeping this optimisation when the code changes. Sticking with the example, suppose you have code like this in some hypothetical (1) language that allows you to express ideas but optimises them the best it can, where `x` and `y` are Strings still:
var frobozz = x + y;
var frobozz = x + y;
/* skip a couple dozen lines of code */
var gunther = x + z;
So don't be sad! It just depends on what problem you want the language to solve for you.
As for commercial versions,
https://www.cincomsmalltalk.com/main
https://www.exept.de/en/smalltalk-x.html
https://www.instantiations.com/vast-platform
And its IDE spirit lives on Java IDEs and Visual Studio Code (as Erich Gamma is on the team).