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Q&A with Matz

by Evan Phoenix and Yukihiro "Matz" Matsumoto

The video titled "Q&A with Matz" features Yukihiro 'Matz' Matsumoto and Evan Phoenix at RubyConf 2014 discussing various aspects and future directions of the Ruby programming language, particularly regarding Ruby 3. The conversation centers around static typing, potential language changes, and the evolution of the Ruby standard library.

Key points discussed include:

- Static Typing: Matz expresses interest in static typing, emphasizing the need for experimentation. The discussion touches on defining types through methods rather than fixed declarations, akin to Go's interfaces, and the role of type inference in enhancing code usability, especially for IDE auto-completions.
- Language Compatibility: Matz highlights concerns about creating compatibility gaps when removing features in Ruby 3, comparing it to Python's transition from version 2 to 3. He considers the implications of dropping certain global variables and quirks.

- Standard Library Maintenance: There is a consensus that Ruby 3 should consider deprecating unmaintained parts of the standard library. This involves evaluating components that are outdated and might be removed gradually.
- Threading Model: The discussion includes the ongoing debate about Ruby's Global Interpreter Lock (GIL) and threading abstraction. Matz presents the idea of a higher-level concurrency abstraction to improve usability, even suggesting a compiler option to illustrate the challenges of writing thread-safe code without the GIL.

- Future of Macros and Git: Matz firmly states that Ruby will not incorporate macros in Ruby 3. The possibility of migrating Ruby core development from Subversion to Git was also addressed, contingent on team agreement.
- Threading Ideal Model: Future threading models were discussed, including the actor model and concepts like immutable objects from other threads. Matz also compares Ruby with other programming languages like Rust and Go regarding their philosophies and technical capabilities.
- Static Analysis and Community Input: Looking ahead, Matz indicates an intent to release tools for static analysis related to soft typing, encouraging community input on future Ruby implementations.

In conclusion, the Q&A reflects Matz's commitment to evolving Ruby while maintaining its core principles and ensuring community engagement in decision-making processes. The focus on experimenting with features like static typing and improving threading illustrates a desire for Ruby to adapt to modern programming needs while also looking out for the long-term usability and stability of the language.

00:00:18 So, there were a lot of questions about Ruby 3, which makes sense. I can handle that. Someone asked a question about static typing.
00:00:32 There are multiple questions there. One could be, are you serious about static typing? It really depends on what you mean by 'seriousness.' I like the idea.
00:00:52 You've parsed my intent well, so that’s good. It’s an interesting idea; would that be a fair statement? But if it doesn't pan out, then it might not happen.
00:01:12 We have to experiment with it. I found it very interesting to watch you describe it and mention the fact that...
00:01:39 An example showed a call to `to_int`. If you wanted that to have a static type, what type would you expect for it? This would be easier if I had code to describe it; talking about code in words can be cumbersome.
00:02:19 You would have a method that takes an X, and inside that method, it calls `x.to_int`. What kind of type do you expect X to be responsible for in the method declaration?
00:02:41 In my mind, I expect X to be a #{some_type}, I mean I expect it to be able to respond to `to_int`.
00:03:11 So the type is described by the set of methods it can respond to. Are you thinking of it like Go’s interfaces, where you would define a requirement without saying exactly what type it is?
00:04:02 You wouldn’t say that X is a fixed number because you don’t care, you just need it to have `to_int` available.
00:04:26 You bring up an interesting point. Would you define that as a separate module that just has one method in it, or would you use some construct to describe the signature you want?
00:05:01 Yes, but it would be created inside the compiler, so it would never be exposed outward.
00:05:34 In that particular case, something would check that `to_int` is defined when you call it on X. Would the programmer be expected to add type declarations, or would you prefer more type inference?
00:06:14 Yes, more of a type inference approach sounds interesting. The compiler might provide some information about expected types.
00:06:35 This is all for video clarity. The IDE could use that info for auto-completions or something like that.
00:07:05 You consider that in type inference, it would bubble back up as well, meaning if I passed X as an argument somewhere else, would the requirement for `to_int` propagate back up the call stack?
00:07:51 Yes, that would be interesting.
00:08:29 So if the variable X stated that it needs to respond to `to_int`, that informs the type of the variable, reflecting a kind of conformance.
00:09:13 You're focusing on conformance rather than worrying about runtime performance, correct? This way, when Ruby files load, the compiler can point out potential methods that wouldn’t work.
00:10:12 We had another question: since Ruby 3A might be a good time to remove features while adding others, do you have anything in mind that you would want to remove?
00:10:43 Possibly some of the power inherent in global variables. For example, `$variable`. I’m considering getting rid of some more quirks in the language, but I'm not sure yet.
00:11:25 The last thing I want is to create a huge compatibility gap between versions, like we saw with Python when moving from 2 to 3.
00:12:06 It’s been successful so far with Ruby 2 because of how it allowed dropping replacements to previous versions.
00:12:22 This also applies in some way to Ruby 3.
00:13:23 Now, what about the standard library? There’s been an ongoing effort to ensure there are maintainers for different parts. Some are maintained while others aren’t.
00:14:01 Do you think Ruby 3 is a suitable time to pull out parts of the standard library that aren’t actively being worked on?
00:14:50 We’re in the process of gamifying the standard library. Back in early Ruby versions, we added a lot of functionality because of the battery-included philosophy, and we didn't have RubyGems yet.
00:15:36 These parts have since become outdated and there are some that have gone unmaintained. We need to gradually remove what’s unused.
00:16:25 Sure, it will happen, but maybe in a Ruby 3 or later.
00:17:04 It’s a matter of evaluating what’s still relevant and beneficial.
00:17:31 I am glad you brought up the idea of thread abstraction. We’re still thinking along those lines.
00:18:02 We haven't reached a conclusion yet, but both Koichi and I have strong opinions on the matter.
00:18:55 We do agree that adding a higher-level abstraction for concurrency would be beneficial, but our ideas differ.
00:19:27 In the last year or so, the emphasis on the global interpreter lock (GIL) has changed. People seem to have strong opinions about it.
00:20:12 While the GIL protects users by allowing safe threading, it has led to complaints. I asked to prepare a compiler option to turn off the GIL.
00:21:03 It would demonstrate how difficult it can be to write a thread-safe program without it. It's been quite a challenge.
00:21:44 At present, the parts of Ruby that are thread-safe still run with the GIL. What is run without it is much more limited, such as system calls.
00:22:38 There are still complaints about the GIL, although many parts of Ruby rely on it.
00:23:20 I believe that we need higher abstraction; the current threading model is too primitive for many users.
00:24:06 How about embedding a Ruby interpreter inside C Ruby? Imagine actors running independently, while C Ruby coordinates them.
00:24:51 Actually, there's a guy who wrote an extension that allows embedding Ruby within Ruby on its own heap.
00:25:40 Now, about macros, we received a common question every year regarding Ruby 3 having macros. The answer's straightforward: no.
00:26:23 The short answer is no; the longer answer is still no.
00:27:09 When do you think Ruby core will migrate to git? We've been on Subversion for years.
00:27:56 I'm not sure yet. The coordination team is quite reliant on scripts written around Subversion.
00:28:54 We have a lot of pull requests and issues on GitHub after all. If the majority agrees we can move to Git, it could happen soon.
00:29:43 I also want people to know how you personally use git.
00:30:20 I used to work with quilt and now use G, which is a stack-like tool to organize git commits.
00:30:59 It allows for flexibility, like naming and changing the order of stacks, making it very handy.
00:31:39 Looking at threading in Ruby long-term, if you could envision an ideal threading model, what would that be?
00:32:15 There are many ideas regarding whether to follow the actor model or impose thread association per object.
00:33:09 Koichi suggests that objects should belong to the thread that creates them, meaning only that thread can modify the object.
00:34:01 Objects from other threads could be treated as immutable. For instance, you could grant limited access but not modify.
00:34:49 How about Rust? Have you looked at it? What do you think?
00:35:29 Rust combines system programming with functional programming languages comfortably. I prefer Go for its simpleness.
00:36:10 What are your thoughts on changes to Ruby's syntax to explicitly state a method should or shouldn't return a value?
00:36:51 It’s a complex issue worth exploring. If it could segregate methods that should not return values effectively, that could be interesting.
00:37:39 I've encountered unexpected behaviors because of overloaded return values I’d like to fix.
00:38:13 I have found unbound methods quite fascinating; they allow for methods to be invoked without attaching to an instance, allowing for more dynamic behavior.
00:39:02 Yet, when we bind them, they still check if the object receiving the binding is an appropriate ancestor.
00:39:46 It seems like this experimentation could deepen understanding of Ruby's object system. Do you want to add anything?
00:40:27 Your feedback on soft typing would certainly be beneficial when considering future Ruby implementations.
00:41:18 I plan to release tools for static analysis related to soft typing soon, looking forward to the community's input after that.
00:42:05 The Ruby ecosystem expands—each implementation serving a different niche can lead to a more vibrant community.
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