This happens with all corporate software, as people compete to (for instance) foist their new videoconference system into your calendar flow. That's sort of tolerable for end-user software, but horrible for programming languages where feature-feature interactions grow as N^2.
One notable remaining exception to this trend is Go. They are committed to the "simplicity" mantra and so far they have stuck to carefully weighing and discussing any feature added to the language. I know that some consider it too simple and the "glacial" pace of development not exciting enough, but I personally appreciate it...
Apple it seems does well w/ a Scott Forstal or a Bertrand Serlet running cover for their engineers. maybe not so much if there's a giant committtee....
And before that Avie Tevanian.
After that it was Craig Federighi. And I dont like the decisions and directions since then to say the very least.
Sometimes I still think about Bertrand Serlet leaving, the year that Steve passed away or 6 months after Steve took leave of absence. I wonder if he saw what was coming and simply decided it was time to leave.
And this is pure kremlinology at this point, but I feel like Apple Music, at least the client part, has to go back under Craig and not Eddy....
Committees work when they have a shared vision, and a base strong enough to keep them on that path.
It’s clear from Lattner’s statement that Apple have moved that vision, have not brought the group along with that change and the result is wasted effort and a passive aggressive approach.
I would posit that rather than operate as a committee, instead that leadership is being exercised by a limited few and the structure is being retained as a fig-leaf :(
It is not the most efficient way to do things. It explicitly sacrifices some of it to help prevent leaders with uncontested power from coming up with things like concentration camps for dissidents.
The point of civil disobedience isn’t to avoid jail, it’s to show you believe so strongly in your cause you’ll go to jail anyway, so people will listen to your cause and maybe sympathize.
If we skip the step where civil obedience doesn’t result in consequences then we remove its signaling power and it just leads to a race to the bottom.
Justin Trudeau: "When a government starts trying to cancel dissent or avoid dissent is when it’s rapidly losing its moral authority to govern"
AKA Protest is terrific only when it doesn't happen in my backyard. Trudeau had no problem supporting "illegal" protests which blocked roads and essential supplies in other nations.
People say all kinds of things without really having a vision or philosophy behind it. It's just how they feel at that particular moment. Unfortunately most societies offer more reward for easy answers and saying what people want to hear then staying consistent.
Software engineering is largely non value based, they are technical based. On things they designed for and on things they base their code upon. In such affairs, democracy is a incompatible framework. It's like my c++ compiler does not compile Java code, that's a technical design and facts. It has no implications to anything political.
You can call it a moot point since the amount of what you can do in pure C today is very limited - you have to use at least a few libraries to do anything remotely useful even on very light systems, but in today's fast developing tech world it's one of these things that really stand out.
There's just so much prior art out there.
You might find this an interesting perspective:
Having a core language helps a lot too. E.g. I don't expect Rust to go off the rails.
For instance sync rust is mostly nice to work with, but async is another story entirely. I have the impression that it was somewhat rushed into the language due to community demand, but it's not really a fully solved problem.
My understanding is this is a FUD meme that has been passed around. Async isn't finished yet, but was debated for years and considered with incredible care and input from the community.
more context in the comments here: https://news.ycombinator.com/item?id=26406989
specifically https://news.ycombinator.com/item?id=26407565
Surely you want to use the pure rust async aware postgres client and the pure rust grpc implementation, but with async that's not a free choice.
You now have to deal with the fact that these (actually often quite well written) reimplementations often lag quite a bit in functionality.
For example you think you can just use some boring technology like a RDBMS but then you discover that pgbouncer doesn't really work well with sqlx. Similar stories for gRPC and other stuff.
Don't get me wrong, I'm not saying that's because async implementation is bad or it hasn't been well thought out. Other languages make other tradeoffs (e.g. Go detects blocking syscalls and increases the size of the thread pool, which makes it a bit easier to accomodate blocking FFI with the core async model, but that comes with a price).
What I'm saying is that in practice async rust feels like another language, a language built on top of rust, that looks like rust, that can call rust, but effectively creates its own ecosystem. The problem is compounded by the fact that it's still called rust, and often you can write libraries that can do a bit of async or not based on optional features.
It's probably all unavoidable and for the better, but it does add a source of fatigue that must be acknowledged and not dismissed as FUD.
In return, of course, you get a style of concurrency that tends to be much easier to reason about and much less prone to subtle bugs than traditional preemptive multitasking.
Whether that tradeoff is worth it is obviously very dependent on the particular situation.
I'm not sure what the GP meant, to be honest. Async "colored" code does have an tendency to "infect" more and more of your codebase, but you can still write and integrate big chunks of non-async code (e.g. a parser or a network protocol) if you're mindful about your design.
I could be wrong though. The reason I like to discuss these things here is the opportunity to be proven wrong by someone who knows more and offers a counter-example
https://docs.rs/tokio/latest/tokio/task/fn.spawn_blocking.ht...
But you need to know when you must call this and when it's ok to not call it.
The type system won't help you with that. But if you forget to call it you can cause starvation and if you call it too often you may create too many threads.
What I see in the ecosystem is that such tricks are perceived as hacks and that it would be just better if one could just write a pure rust reimpl.
Surely there are enough reasons that drive people to reimplements stuff in rust. I think this aspect of async nudges people even further into that though.
Still, the fact that Rust has MIR I think very much limits the damage premature async can do. If we get something better, it should be quite possible to extra "Rust - today's async" to recreate it.
Conversely, I wouldn't be surprised if many of the misfeatures in Switch are in impossible to extricate.
[^1]: https://blog.rust-lang.org/inside-rust/2022/02/03/async-in-2...
Unless the rails are too rusty :-)
You would have 2 lines of code per property but one fewer concept—and I think that is a much more important factor. To me—this was not the right way to add sugar.
When I started, I thought it would be some complicated beast, but no - its a reasonably simple and elegant C superset with the only disadvantage of some extra verbosity. (but Apple API's suffer from verbosity as a principle)
I have to wonder: why did Apple create Swift ? Objective-C is quite nice, especially for C/C++ programmers. With Objective-C++, interop with C++ libraries is also terrific. Swift offers nothing like this yet.
I asked this many times over the years, even in this thread [1]. Still no concrete answer. I still think overall it is a distraction.
So Apple needed a nice language with C-like syntax to woo developers.
They wanted a safe, performant language that interoperates with Objective-C. Safety gets them fewer vulnerabilities, interoperability means they can gradually decrease (Objective-)C usage.
Also:
- opinions on the nicety of Objective-C differ (but the only arguments I’ve heard why it would be bad more or less are “I don’t like the syntax” and “it’s verbose”, both of which, IMO, are weak. Both, IMO, are acquired tastes. I don’t think anybody is born preferring terse K&R C, for example.
- as you probably know, work is being done on C++ interop (https://github.com/apple/swift/blob/main/docs/CppInteroperab...), so that may improve.
NSString *string1 = @"Some";
NSString *string2 = @" string";
NSString \*string3 = [string1 stringByAppendingString:string2];
For sake it was built nearly 40 years ago. Not sure if there's any room to question why Apple and devs wanted a new language.
I was amazed why anyone would want to use this language before Swift but people didn't have a choice.
There were efforts like MacRuby.
https://www.mikeash.com/pyblog/friday-qa-2015-11-06-why-is-s...
It is amazing that people forget to simply use the right tool for the right job and blame the PL instead.
Because a dependent type is a type that represents a computation. A word that symbolises a computation, a word which can be manipulated by hand and assured by machine – and vice versa.
Software is automation. Types are signifiers of meaning. Dependent types are the automation of the automation.
Using a dependently-typed language feels like handling a machine which is the result of having closed a fundamental loop of expression vs. meaning. And that is what it is.
It’s very philosophical-sounding! It has its roots in philosophy – in intuitionism, where math dug down and met philosophers who had dug down from the other side. Kind of.
Practically, the upshot is that things actually become simpler. Kind of because you can grip the tool everywhere. Un-dependently typed languages feel kind of like they’re part tool, part void. You usually can’t express things relating the context you’re in, or looking at.
(As I see it – at least these days – dependent types just are. It’s very, very nice to just have higher-order unification and the things that sort of fall naturally out of having it.)
I found this talk from Xavier Leroy a while back too: http://www.cs.ox.ac.uk/ralf.hinze/WG2.8/26/slides/xavier.pdf. He is the main person behind CompCert, the formally verified C compiler. They do that verification in Coq, so I was expecting him to be a believer of dependent types. But he had this to say:
“ Dependent types work great to automatically propagate invariants
- Attached to data structures (standard); - In conjunction with monads (new!).
In most other cases, plain functions + separate theorems about them are generally more convenient.”
For that reason I prefer Isabelle/HOL as a theorem prover. The core logic is simpler, but you can express whatever you want as a theorem, without worrying about phrasing it within the type system. It feels a lot more natural.
That’s not without downside either of course. Proofs in Isabelle notoriously must match the structure of the code being verified, so changes to the code require proof changes. Liam O’Connor wrote an example of where they he feels dependent types are better here: http://liamoc.net/posts/2015-08-23-verified-compiler/index.h....
Even with that, I’d rather have simple code plus simple propositions with complexity at the proof level. This will likely be another eternal holy war though.
It helps me see what I think I’m seeing, or rather to define it. It also has helped me to perspectives I hadn’t seen.
I’m coming to dependent types from here: “simple, clear code good yes program program argh I can’t express a very distinct thought without escaping to another language layer or generating code using string concatenation”, and from here: “my data structure is simple and clear but argh it needs a handwritten parser and serializer and it needs to be maintained and argh why am I writing a parser AND a serializer it should be just one bidirectional definition? and argh why do I need to write it for each output/input format?”, and from here: “my code is simple and clean and my variables are well named and my tests are well defined and my documentation is well written but argh why can’t I just fold the mechanics that the tests define into the code? as proofs? (and… argh? why can’t my variables and documentation and method names be checked against the code?)”.
It’s metaprogramming that I’m thinking about. And most programming ought to be programming. But we definitely need metaprogramming, and it needs to be understandable and composable and simple and clear. And I don’t know if dependent types are a complete solution to that, but I do think that they are necessary for it.
That-which-is dependent types, which by definition is a computation of what it is and is a proof of what it is. Those philosophical terms finally become practically grounded and practical help in a lot of the work I find myself doing.
I’ll certainly look for the false idol too! My sincere thanks.
> Software is automation.
Looking forward to C# 11 code.
Wider question: How can a language and its core library stand still? To me, standing still is death for any computer programming language ecosystem. Many languages are just getting started on the idea of "green threads" and "colours" (sync vs async). Some of this can be done purely with a core library using existing language features, but some evolutions are better done with language features.
> How can a language and its core library stand still
I guess by having a more abstract foundation and relying less on adding hacks like colored function? Haskell seems to be like that.
Another thing is language extensions that you have to turn on to use. This makes deprecating stuff easier in the future, so languages can trim itself instead of keep growing.
I would almost never write C++ (in the context of low level and performance-relevant code; I write a lot of things for a lot of stuff) if the type system was a touch more rigorous (why can't I specify, and have the compiler yell at me if I don't properly handle, "this pointer may never be null"? TypeScript can do this kind of type narrowing in its sleep!) and if error handling/lifecycle cleanup wasn't hazardous (I'm not even saying exceptions and try-catch, just make it easier to guarantee that a cleanup clause gets called when leaving scope, like Ruby's def-ensure-end).
As it is, whenever I finally hit the breaking point with C++ (which I write mostly from inertia because I know it pretty well) it's probably Rust for me.
I am a fan of Rust, but I am not 100% sold on it. The safety features and ADT's are nice, but I find it quite clunky in practice, and it is just such a huge language full of so many features. It almost feels more like a test language to try the concept of static memory management than a properly designed language in some ways.
I feel it's missing the quality from C/C++ that they are a very thin abstraction over assembly.
I think this statement implies that it’s clear and obvious what assembly will be generated from a snippet of C/C++ code. But few people can understand everything that optimising compilers and modern processors do to normal looking code. An example of this lack of knowledge is seeing people disagree on if a snippet contains UB or not.
If C is so simple, why do people struggle to write it?
Well when I'm talking about an abstraction over assembly I'm not talking about optimizing compilers. That's another topic entirely. What I mean is, if you look at a block of C code, it's very easy to understand what the machine is doing.
> If C is so simple, why do people struggle to write it?
Do they? I think people struggle to write correct, bug-free code in C, but that's because it doesn't save you from yourself, and it's happy to let you do whatever the hardware will do. That's a much larger programmable space than the set of all safe correct programs.
But I don't think people in general have difficulty looking at a snippet of C code and understanding it.
So they simultaneously understand what the machine is doing but don’t know what assembly will be generated? Both can’t be true.
If everyone understood what the machine was doing, everyone would be able to look at a snippet and agree - “that’s UB, let’s not do that”. But they can’t agree. Because few people understand what the compiler and the processor will do.
The “thin layer of assembly” was true for the first generation of C compilers. But it hasn’t been true for a long time. It’s a complete black box now. Anyone who thinks that it’s straightforward isn’t being upfront with themselves.
I mean I can understand a reasonable mapping to what the un-optimized assembly would be. Compiler optimization is very complex, and is going to obscure the results in every language.
> If everyone understood what the machine was doing, everyone would be able to look at a snippet and agree - “that’s UB, let’s not do that”. But they can’t agree. Because few people understand what the compiler and the processor will do.
What? I think everyone can agree that UB is much harder to detect in assembly than in higher level languages than assembly, and assembly gives the most clear view of what the machine is doing. It's a very complex topic to create a system which detects and disallows UB automatically in the compiler - this requires a lot more complexity than a simple mapping of high level instructions to machine instructions.
> The “thin layer of assembly” was true for the first generation of C compilers. But it hasn’t been true for a long time. It’s a complete black box now. Anyone who thinks that it’s straightforward isn’t being upfront with themselves.
I don't know, seems pretty straightforward to me: https://godbolt.org
Can you look at a non trivial C code base and make such an assertion? You can’t. Even simple looking C code could be translated into problematic assembly because such a transformation is technically valid. And it’s beyond the ability of anyone but an expert to guard against that.
C is a very useful language. Very important. Very fast. A great tool in the right hands. The world wouldn’t run without it. And it will remain useful and important and fast for decades to come, certainly. But it’s not simple and hasn’t been for a long time. Let’s acknowledge that.
Do you agree that this statement implies 2 things
1. The compiler isn’t doing anything unusual or unexpected. It applies only basic, easily understandable transformations from C to assembly
2. An intermediate C programmer would be able to guess correctly most of the time what the generated assembly would look like. And thanks to this, such a programmer would be able to avoid most footguns.
But the compiler does unusual/unexpected things, and it’s hard to guess what assembly will be generated or what that assembly does, it’s not a “thin abstraction”. Would you agree?
I think a better metric is: an average CS grad with a little bit of background in compilers and assembly could reasonably be expected to be able to write a naive C compiler which covers say 80% of the footprint of the core language on their own in a matter of weeks.
What do you think is the size of the cohort of people who could write a naive Rust compiler, with borrow checking, ADT's, traits and non-lexical lifetimes? Even without some of the fancy bits like async you're already talking about grad level CS topics at the very least.
I don't find the idea of a new non-memory-safe C replacement in 2022 very exciting. We should be moving away as an industry from non-memory-safe languages, for the obvious security and productivity reasons.
We can argue the thinkness (or the thinness) of the abstraction until cows come home, but
while (*dst++ = *src++) ;
L1:
movb @(r0)+, @(r1)+
tstb (r0)
bne L1
*ptr &= 1;
and #1, (r0)
C++ is much less of a hardware abstraction, specifically when it comes to the higher level language features.
Or 8 bit CPUs like 6502 and Z80 that aren't even able to fully support C.
Yes – historically – C has never been a perfect fit for 8-bit architectures as it had been conceived for a 16-bit architecture. So what? There are C compilers for 68HC08 68HC11 MCU's as well.
Yet, C has outlived «many languages offering the same "low level" capabilities of C».
And if you index into an array in C, that's basically like saying `root memory location + stride * index`. In Rust it's calling a trait function which could be doing arbitrary work.
Rust and C++ are on similar levels of abstraction, but C is much, much simpler.
And it's certainly true that Rust has overloading and C doesn't, but that wasn't what I was getting at. The point is that C is defined in terms of the C virtual machine, not the underlying hardware. The C virtual machine is quite far from the actual CPU instructions.
Rust is clearly not at a higher level of abstraction than C++, yet in your own argument you've put C and C++ on the same ground…
> I feel it's missing the quality from C/C++ that they are a very thin abstraction over assembly.
> Rust and C++ are on similar levels of abstraction, but C is much, much simpler.
Read [0] for a comparison among Zig, D, Rust, and C++, and read [1] for a deeper look at the language's goals. I personally really love Zig's type system [2], with a system for generics that is very simple and consistent.
[0]: https://ziglang.org/learn/why_zig_rust_d_cpp/
[1]: https://ziglang.org/learn/overview/
[2]: https://nathancraddock.com/blog/consistency-in-zigs-type-sys...
We knew about many of these features then, when C was created - but it wasn't until the 2000's really where computing horsepower caught up to be able to use them in a universal way.
You can do so easily. A reference is a pointer that is never null.
This isn't even theoretically true:
void blah(int &x) { x++; }
int main() {
int *x = NULL;
blah(*x);
}
So it will crash, whether that's undefined behaviour or not. The thing at issue here is that other languages have reference types that are more strictly statically guaranteed to be non-null. My point is that references are not a substitute for those, because holding them wrong is not only easy, it's extremely likely to happen in code of any reasonable complixity that mixes pointers and references (ie. almost all production C++ code).
>I would almost never write C++ …
Edit: nevermind, I missed the point! GP is saying he wouldn’t write C++ if C supported these features.
C23 is about to
- add keywords that was valid identifiers before
- remove K&R parameter syntax
- change semantics of the most popular function argument list declaration
- forbid representations other than 2's complement
A good deal of bad code design comes down to not being able to predict what a bit of code is going to do without stopping everything, unrolling whatever built up state you had in your mind (from the thing you were actually trying to do) and sit and become one with the code for a time. But at least when you’re unsure what the code is doing you have a suspicion that is the case. The worse sin by far is misdirecting you into thinking it does one thing when it does something else, or even the opposite.
We like to complain about extroverted business people interrupting us, but we seem to have very little guilt about doing it to each other by leaving these sorts of time bombs in our code.
For all the critique of java, I think this is the one thing java got correct. It is (no matter how verbose or clunky) still easy to read and understand.
Of course one can't make them understand as they are just following "best practices" enforced at employers.
First of all, in most IDEs, it's very quick to jump to a function's actual definition to investigate such questions as "What if both of the arguments are < 0?" or "Is null an acceptable argument?". With annotations, you'll often go-to-definition and be staring at an almost empty class that hopefully has a docstring. This is because the annotations, themselves, don't actually do anything- you have to go find the code that actually checks for the annotation and does stuff.
In my experience, the docs are often not good enough when I run into a problem. I was wrestling with some strange behavior with JacksonXML some time ago, and I had a very hard time figuring out what went wrong because Jackson has so many options and they don't actually all compose well, so it's not even about figuring out what one option/annotation does- it's about figuring out what happens when I set OptX=1 and OptY=4 at the same time. Unfortunately, the docs only tell me what is supposed to happen when OptX=1 and what's supposed to happen with OptY=4, but nobody has decided to document every single combination of every single setting in the library.
Could you give an example for your point?
It was impossible to properly trace any behavior through. Every method zigged and zagged through the inheritance hierarchy multiple times as you traced deeper. And so:
> It is (no matter how verbose or clunky) still easy to read and understand.
The sentiment is taken well, but it's just not true. Credit your fellow engineers for the positive experience, not any particular language.
And I would add that Go is obviously easier than Java here by design, but anyone could write a horribly over-abstracted Hello World or Fizz Buzz in any language given the motivation.
Nothing in golang makes it easier to understand compared to Java by design, and the opposite is actually true (e.g. no proper enums, no records, no pattern matching, etc.) make it more verbose and harder to get to the underlying logic.
That being said, you should see some of my employer's golang code with their web framework that they wrote and the 80+ line stack traces.
The best part was the perfect C/C++ interop. When I was working on iOS apps in Objective C, I found myself writing a lot of pure functional code using C and it was pretty neat to be able to integrate that with the OO stuff from Obj C so easily and with a clear dividing line.
I think that this comment was written with a positive spirit, but that quote-chopping is incredibly meaning-distorting in a way that counters your point. The original poster stated that Swift "used to be the case that you could look at a piece of Swift code and roughly understand how it would compile to assembly pretty easily" -- you chopped after "understand". There are very few languages where it's /harder/ to understand how they compile to assembly than Java. The JIT compilers are both incredibly complex and incredibly varied, and almost all of them have multiple possible compilation outputs for the same code.
Java, as a language, has been relatively successful in making it easy to understand programmer intention when reading code, as your chopped quote implied -- but the same could be said of Python, Julia, and plenty of others. Swift is in the much smaller category of languages where you can understand how the code will /run/ -- along with C, etc. One could argue that Swift's greatest virtue is that it falls into both categories, but that's another discussion.
Not many people these days can read and fully understand the 64-bit assembly code generated by llvm. I think it is less than 1% of Mac developers.
C++ also have a lot of magic going on. Even C can be tricky with an optimizing compiler.
I don't know what percentage of developers can read assembly, but the popularity of tools like Godbolt strongly suggest it's non-zero. In my own experience, all of the most skilled developers I've worked with have been comfortable digging down to the necessary level -- and doing that in Java, or most other JIT'd languages, is just not fun.
You'll notice that I very much didn't put C++ on either the "easy to understand intent" or "easy to understand behavior" lists -- while it's my preferred language and my primary language, ease of understanding is not its virtue. And while I agree that C compiled with a minimally optimizing compiler (CompCert, clang -O1, etc) is easier to understand than optimized code (for me, the sweet spot for understanding is as compiler that does good register allocation and constant folding, but only really does instruction reordering for memory ops), it's pretty rare that I look at the output of highly optimized code and am surprised or find it hard to follow. Some constructs (medium sized switches, for example) can be pain points... but most often reading assembly output from optimized C is either "yeah, that's about what I would have written" or "close, but you missed this optimization/intrinsic, I'll do it myself."
Yep. If anyone had doubts that the language was no longer the one Lattner designed, SwiftUI should've put the nail in that coffin.
Swift is an imperative, statement-oriented, language. In fact, I get kind of frustrated when writing Swift after spending some time with Rust: I just love writing `let x = if foo { 1 } else { 2 }` or `let x = match foo { ... }`, and it's ugly as hell to try to assign a variable from a switch statement in Swift, etc. BUT, that's okay- I'm almost sure that zero programming languages were written with my opinion in mind, and Swift is Swift.
But, SwiftUI is declarative, which just doesn't work with literally the entire rest of the language. So they added result builders and these weird, magical, annotations just so we can have a UI DSL.
Error handling is now inconsistent and annoying, too. The original approach was to use this quasi-checked-exception syntax where you mark a function as `throws`, and all callers are forced to handle the possibility of failure. The difference between this and Java's checked exceptions is that the specific error type is not part of the signature and therefore the caller only knows that they might get an Error, but not what specific type of Error.
They even have a mechanism for higher-order functions to indicate that they don't throw any of their own errors, but will re-throw errors thrown by function arguments. Clever.
Okay, fine. Pros and cons to that approach, some like it, some don't, etc, whatever. Except then they realized that this approach falls flat in some scenarios (async/promises), so we really just need to go back to returning error values. So they stabilized a Result type.
So, now we need to figure out when we're writing a function if we want to return a Result or make it throw. And, even more annoyingly, Result has a specifically-typed error variant! It's actually a Result<T, E>. Which is it, Swift team? Should immediate callers care about specific error types or not?
Just recently, they landed the async and Actors stuff. Async is fine and great, and is consistent with the imperative syntax and semantics of the language, and it even supports `throws`, IIRC. But Actors? What the hell is that? That's totally out of left field for the rest of the language.
I used to really enjoy Swift in the 2.x to 3.y days, but it really seems like it doesn't even know what it wants to be as a language anymore, which is a real shame- it had a real shot to take the wind out of Rust's sails, IMO (The number one "scary" part of Rust is lifetimes and borrow checker. Swift has CoW structs and auto-ref-counted classes, instead, which can be seen as more appropriate for higher level tasks than writing system libs, etc).
I think the main issue with GCD is the potential for deadlocks in serial queues (which it doesn’t really help you with), and the related problem of thread explosion in concurrent queues.
Actors make protecting shared mutable state really easy, solving a big chunk of the reason you’d want to use semaphores and serial queues in the first place. If you stick with async/await/Task{}/actors, you’re guaranteed to only have the optimum number of threads that can saturate cores, and won’t have deadlocks. If you use Sendable properly and heed all the warnings, you’re a good way towards the kind of “fearless concurrency” that Rust gives you. It really is pretty great IMO compared to GCD.
I’m actually happy with this decision… it was very much done intentionally to prevent the kind of thread explosion that is all too common in GCD. The criticism of GCD I linked to was very skeptical of actors for this reason; if the implementation decides to add more threads to avoid deadlocks, you get the same performance pitfalls as in GCD, and thankfully that didn’t happen.
In practice, I’ve found that avoiding deadlocks is as simple as grepping for `DispatchSemaphore|DispatchGroup` in your codebase and eliminating them with extreme prejudice. If you stick to Tasks/TaskGroups/Task.sleep, there’s no real possibility of accidentally introducing deadlocks unless you try really hard to do so.
And yeah, logical races can still happen in actors, but it’s easy enough at a glance to tell whether you’ll run into one… if you avoid using `await` in a section of code that needs to run exclusively, you’ll be fine. (Even with `await` calls you may get lucky if there’s no actual suspend point happening, but a quick and dirty rule is just “don’t call await and your code will never be run concurrently.”)
You’d think so but then you realize that framework code you call into might decide to do this and you wouldn’t know until it deadlocked. On a 6-core iPhone 13 this is probably not going to be noticeable, but that’s probably not true on a 2-core iPhone 6s…
But if you’re calling into framework code which is using GCD, the queues it dispatches into will be run on a separate GCD thread pool. If said framework code is using a semaphore or lock to block your calling (Concurrency) thread, then it stands to reason there’s another thread in the GCD pool which will eventually unlock it. (Or else it’s a deadlock no matter what you do.)
I haven’t come across any framework code which violates this, although maybe you’ve run into problems I haven’t.
That said, I'm really not sold on actors. I think CS as a whole hasn't really landed on the right abstraction for concurrency yet, actors seem a bit experimental, and GCD is plenty good enough in most cases.
But I think it's over-sold as a systems/low-level language. Relying on ARC for all reference types creates a significant floor in terms of performance which makes it unsuitable for a lot of systems programming applications - unless you resort to unsafe Swift, in which case you're not really writing Swift.
What do you think the ratio between people who want to understand what the assembly will look like, to people who want a simple and powerful way to write apps? I think it's very close to 0.
As someone who was heavily invested in Swift, and an active member of the community from around 2015-2019, I'm a bit sad to see the direction the language is taking.
From the time I started experimenting with Swift, I absolutely loved the philosophy of the language. It seemed to really prioritize having a set of well-factored systems, each with their own very rationally designed interfaces, which could be composed to do really powerful things. It was an incredibly expressive language which allowed for writing code with an incredible level of clarity - when writing Swift code I always felt I was writing at the level of the problem domain, not writing syntax. At the same time it offered really nice features for ensuring safety and correctness, like ADT's and best-in-class nullability syntax.
It was a language which sometimes seemed to move at a glacial pace, but the implicit tradeoff was that when a feature landed, it was for the most part very well thought out, and would add to the language with minimal negative impact.
A few years ago that seemed to start to change. From my perspective, some of the features added to the language to support SwiftUI - specifically property wrappers and function builders - very much felt rushed and forced into the language based on external deadlines. And imo they have a largely negative impact on the language: it used to be the case that you could look at a piece of Swift code and roughly understand how it would compile to assembly pretty easily, but with these new features there's a ton of compiler magic going on behind the scenes.