A half-hour to learn Rust
fasterthanli.me
A half-hour to learn Rust
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Re: A half-hour to learn Rust
#2A half-hour to learn Rust
Jan 27, 2020 · 51 minute read · rust
maybe the site's reading time estimator is broken? sarcasm intended.
But seriously, it is good to have people writing things like this.
Re: A half-hour to learn Rust
#3Incredible. Great job.
Oh, I guess it's a year old - but still, extremely good.
Re: A half-hour to learn Rust
#4Previous discussion: https://news.ycombinator.com/item?id=22448933
Re: A half-hour to learn Rust
#5It only took me a couple of hours to port one of my old C programs, an utility to produce a hexadecimal and ASCII dump to Rust. The Borrow checker didn't even faze me. All I needed was plenty of Google-fu and my coding skills. JetBrains CLion and git are also very useful tools.
Re: A half-hour to learn Rust
#6In the 9th code snippet that's not an example of variable shadowing, it's just variable reassignment. Shadowing involves variable assignments in different scopes.
https://en.wikipedia.org/wiki/Variable_shadowing
edit: I should've called it "variable redefinition" or something like that I guess, my mistake. Reassignment is definitely not the correct terminology for this.
Still, it's not shadowing because the new binding of 'x' is not effectively shadowing some other 'x' name, it's just taking its place in the same scope. And this is orthogonal to the memory allocation of the assigned objects.
Re: A half-hour to learn Rust
#7Another great resource: https://learnxinyminutes.com/
Re: A half-hour to learn Rust
#8[deleted]
Re: A half-hour to learn Rust
#9In the 9th code snippet that's not an example of variable shadowing, it's just variable reassignment. Shadowing involves variable assignments in different scopes. https://en.wikipedia.org/wiki/Variable_shadowing edit: I should've called it "variable redefinition" or something like that I guess, my mistake. Reassignment is definitely not the correct terminology for this. Still, it's not shadowing because the new bindi…
There is effectively an implicit scope created by the let binding. In rust you can't reassign a variable without it being mut. The two `x`s are separate variables named x and are not at any point mutated. Reassignment would look like this:
let x = 1;
x = x + 1; // You can actually see the scopes, and the progress of variable liveness, if you run the compiler out to the MIR intermediate language:
fn main() -> () {
let mut _0: (); // return place in scope 0 at src/main.rs:1:11: 1:11
let _1: i32; // in scope 0 at src/main.rs:2:9: 2:10
scope 1 {
debug x => _1; // in scope 1 at src/main.rs:2:9: 2:10
let _2: i32; // in scope 1 at src/main.rs:3:9: 3:10
scope 2 {
debug x => _2; // in scope 2 at src/main.rs:3:9: 3:10
}
}
bb0: {
StorageLive(_1); // scope 0 at src/main.rs:2:9: 2:10
_1 = const 1_i32; // scope 0 at src/main.rs:2:13: 2:14
StorageLive(_2); // scope 1 at src/main.rs:3:9: 3:10
_2 = const 2_i32; // scope 1 at src/main.rs:3:13: 3:18
_0 = const (); // scope 0 at src/main.rs:1:11: 4:2
StorageDead(_2); // scope 1 at src/main.rs:4:1: 4:2
StorageDead(_1); // scope 0 at src/main.rs:4:1: 4:2
return; // scope 0 at src/main.rs:4:2: 4:2
}
}
Re: A half-hour to learn Rust
#10In the 9th code snippet that's not an example of variable shadowing, it's just variable reassignment. Shadowing involves variable assignments in different scopes. https://en.wikipedia.org/wiki/Variable_shadowing edit: I should've called it "variable redefinition" or something like that I guess, my mistake. Reassignment is definitely not the correct terminology for this. Still, it's not shadowing because the new bindi…
In the wikipedia entry you provided, there's an example in Rust, similar to the 9th code snippet, that claims it is variable shadowing: