Rust Programming Language Rust KW Meetup, 5 Mar 2019

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From YouTube: Rust 2018 by Mark Sherry - Rust KW Meetup

Description

This video was recorded during the Rust KW Meetup in Kitchener-Waterloo, ON, Canada on March 5, 2019.

https://www.meetup.com/Rust-KW/events/259334630/

The new edition of Rust was released in December, bringing with it changes and promises. Mark Sherry will cover what Rust 2018 means, how editions work, and changed, and what to expect from Rust 2018 in future releases.

Talk written and presented by: Mark Sherry (https://twitter.com/alfedenzo)
Recording: Mark Sherry

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So Russ Trajan came out last December and at the time there's a lot of confusion about what Russ 2018 actually was. So what is Russ 2018? Well, what were you looking at? It is that Russ 1.0 is Russ. 2015 and 2018 is everything that's changed between then Russ 1.31.

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If the compiler are you using supports Russ to Anita, it also supports a whole bunch of other features like a question mark operator and that's useful from a marketing perspective, but that's how people were excited about herself, not the way of looking at it. Is that rust-red haziness a chance to make some briefly changes and waste them to break stability guarantees. Otherwise, so a little over 10 years ago now, Russ Python 3 came out and 527 its end of life at the end of this year and there's a lot of Isis still using Python 2.

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But part of the reason that people dragged their feet was that if you wanted to use Python 3 in your dependencies have been updated to you, you got be compatible with Python 3. You had to wait until they are updated and those dependencies might have other dependencies that haven't updated or perhaps they had to see component that had to be rewritten is understand, rewritten from scratch or using Python 3.

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Yet I don't need to worry about it yet so if this all deleted, optioned just people didn't so there's a lot of concern with Russ 2018, with its backwards incompatible changes that it might also suppose the ecosystem the way that Python did well. Fortunately, that's not the case for starters, both rust 2015 and rust, 2018, the common standard library. So you don't have. Who was the previous II worked? You now have to use different import statements or new statements.

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What's more breasts, 2018 code can use for us 2015 crates even better for us. 2015 crates can use Rus 2018 crates, so it's forced to regular having to apply. You have to have a sufficient recent version of compiler, but that implies like any new language feature. You want question mark operator. Well, you have to have the rest see that support cetera this works, because both editions use the same compiler there's just some flexible comparisons. Oh, is the current crate, Rus 2018? Okay, do this thing differently instead, but they both compile them to all be Mir.

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I'll get stuck together.

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What's more new features will get out into frustrating fifteen as well, assuming they don't require changes that are us 2018 only, for instance, if you want cost generics great, as far as I know, they'll be coming to trust 2015 whenever they come your honor to sink weight, and if he words are only available over us or 2018, because that would be a frigging change.

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You can still use crates the news of sinking the debate. You just can't use them in your own code. If you're running, that's 2015, so what's new in rust 2018, what does it brings the table of the troops and are sufficiently compatible? You can just easily add them together.

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Well, for starters, non lexical, lifetimes I believe this will be back. She trusts 2015, but for now it's for us 2018 only so what are flexible lifetimes?

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Here's a contrived example. So here we've just got a simple new type, wrapper around back into methods first and push.

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In Rus 2018 we can create an instance. We can get the first element print it out some one, and then we can push me over to the list. Great plus 2015 doesn't like this because first is gonna be around to the end of the scope, and that has a beautiful Oro on the age, so you're trying to get a mutable world. When we do the push sorry, you can't have a mutable and immutable poro at the same time, so it fails other times you might have seen.

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This is, if you ever tried to do something like this. With a hash map, I tried to get an element and push it back in or something and Russ 2018. This runs 5 press 2015 does not like it, so that makes a lot of nice rings simpler. This case, maybe you'd be able to get by by assigning to a temporary variable, but module system changes.

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So one big thing: no more external current. Instead, you just have to have symmetry to your cargo towel and hold on actually gets. That's great. You just have to use the great wherever you want it side effects for macros, because you no longer have an external a to attach macro use.

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That doesn't mean you actually have to use the macro, which is a new thing that not have it.

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But that also means that you don't have every macro from every creature that you brought in all cluttering your namespace, you can just bring whatever macro you need for that. Module use is mostly the same so before I get into the half. 2018 works. South beats paying a bit hundred fifteen works, and this is where the module system kind of confuses people, because the way that it works in 2015 is simple, consistent and really easy to activate build wrong mental model about so in rust of 2015. Every time you say, use whatever.

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If routes that path in the route module of your crate or program, rather than looking at things in the current module, when you do next are crate it just perhaps the main space of that crate into whatever module you call Dexter crater. So if you have, you know, sub module and you closer treat there. Everyone else will have to since that module through that creep through sub module.

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This is a job confusion, because the way you'd ask preference to life. Normally it's different than married to reference it through views in Ross 2018. It looks at what's in your current.

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Module either things that you declared there or things of you previously important through use if it doesn't find that double check. Is this any of an external crate so where, before you there's? No that was focusing, but if you just use regex it'll work, if you want to access something in your trainer programs or if you just proceed with create : :, if you need to disambiguate you in previous into the cell phone :, if you talk to your parents, super core phone goes through the same premium. To this new zone, external crate still works.

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You can still call start crate. You can still say macro use external, don't behave the same way. It did you just don't need to anymore.

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For has outside of use they're pretty much the same.

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Paths are all relative to the current module it's set. You can also know just directly reference external crates so before if you did want you to use reg X, but you wanted to access something from it. You have to say : : reg X inside, but you don't need that you can call and coolin anymore.

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So that's that's! Actually really nice.

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So this is just an illustration of no before you do. This may do that.

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We have question mark in macro rules which this actually came out repeats after quest 2018, but it's 1st 2018 Elfi.

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If you're familiar with how the question mark operator works and regular expressions. This is basically the same so there's motivating example. So you've just got a simple macro here, takes its arguments, prints and math one per line and say we watch training, comma, because traffic copies are really handy.

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Unfortunately, our grammar there doesn't match the trade public. So what let us use it there's a couple ways to deal with that you could have a separate match, rules that handles the extra train. Comma, that's up to you. You could use a star at the end, so you can have zero or more trailing commas, but then people putting the lesser number of trailing commas.

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So that's okay!

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Finally, if you use the question mark operator it just zero or one of course you know this works for more than just commas can use it in every situation where you just use this star or plus before in your happiness,.

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Russ 2018 adds three new keywords.

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Nothing stable is using this yeah. Just the signal rate should make it easier to write this in Christ code right now. There's a lot of debate about how a weight should be used. If it should be used at all. Maybe it should be a macro. Do we want something prefix or suffix position? There's a lot of opinions, I'm not going to get into that.

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If you want to hide or amorous there's the RFC there there's also the website. Are we a sink yet I believe that's good place for keeping on top of okay? What's the current state of physic and weight and rust, the other new keyword is try.

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What twine does is changes the behavior of the question mark operator so that, instead of returning from the function, it just returns early value that is early from a blog.

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So in this case, if foo and bar are option in 32s, this rule or I guess result 932 or something else.

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If either there were an error and will return that error to answer, otherwise it will return this on and I believe the artsy's specifies. There suggests that you don't that you have to wrap the resultant okay, but.

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That's Russ, 2018, there's a couple other things, because they're kind of technical I think there's stuff to do with implicit lifetimes and nicer handing of generics. But this is suppose people are excited about. This is stuff that almost likely affect you. I have a lot of time, so I read have talked about how to upgrade your thing to rust, trick 18.

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But if you look at the last link here, I'll be posting the slides to the meetup group. You can see instructions on how to upgrade I've upgraded a couple things mostly by painlessly, except for realizing that okay I've got some tests wrong and now, if it work the best one for us, 2018 is false.