https://github.com/jonathanmccormickjr/learnrustsomemore
https://github.com/jonathanmccormickjr/learnrustsomemore
Last synced: 4 months ago
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- Host: GitHub
- URL: https://github.com/jonathanmccormickjr/learnrustsomemore
- Owner: JonathanMcCormickJr
- Created: 2024-11-02T21:40:47.000Z (8 months ago)
- Default Branch: master
- Last Pushed: 2024-11-17T22:27:13.000Z (7 months ago)
- Last Synced: 2024-11-17T23:22:00.819Z (7 months ago)
- Language: Rust
- Size: 7.81 KB
- Stars: 0
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
# LearnRustSomeMore
By Jonathan McCormick, Jr.
**A notespace for me as I walk through**
* ["A Gentle Introduction To Rust"](https://stevedonovan.github.io/rust-gentle-intro/readme.html#a-gentle-introduction-to-rust) by Steve Donovan ([GitHub link](https://github.com/stevedonovan/gentle-intro/blob/master/src/readme.md)),
* ["The Book"](https://doc.rust-lang.org/stable/book/), and
* ["Programming Rust, 2nd Edition"](https://www.oreilly.com/library/view/programming-rust-2nd/9781492052586/) by Jim Blandy, Jason Orendorff, Leonora F . S. Tindall
## 2024-11-02
Rust's compiler is your friend.
### Some external crates that are interesting:
`diesel`: ORM and query builder for PostgreSQL, SQLite, and MySQL.
`rand`: Random number generators.
`tokio`: an event-driven, non-blocking I/O platform for writing asynchronous applications.
### Borrowing
For some reason this compiles...
``` rust
fn main() {
let var_x = "My string";
println!("var_x = {}", var_x);
let var_y = var_x;
println!("var_y = {}", var_y);
println!("var_x = {}", var_x);
}
```
```
$ cargo run
Compiling learnrustsomemore v0.1.0 (/home/jonathan/projects/learnrustsomemore)
Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.13s
Running `target/debug/learnrustsomemore`
var_x = My string
var_y = My string
var_x = My string
```
... but this does not:
``` rust
fn main() {
let var_x = "My string".to_string();
println!("var_x = {}", var_x);
let var_y = var_x;
println!("var_y = {}", var_y);
println!("var_x = {}", var_x);
}
```
```
$ cargo run
Compiling learnrustsomemore v0.1.0 (/home/jonathan/projects/learnrustsomemore)
error[E0382]: borrow of moved value: `var_x`
--> src/main.rs:8:28
|
2 | let var_x = "My string".to_string();
| ----- move occurs because `var_x` has type `String`, which does not implement the `Copy` trait
...
5 | let var_y = var_x;
| ----- value moved here
...
8 | println!("var_x = {}", var_x);
| ^^^^^ value borrowed here after move
|
= note: this error originates in the macro `$crate::format_args_nl` which comes from the expansion of the macro `println` (in Nightly builds, run with -Z macro-backtrace for more info)
help: consider cloning the value if the performance cost is acceptable
|
5 | let var_y = var_x.clone();
| ++++++++
For more information about this error, try `rustc --explain E0382`.
error: could not compile `learnrustsomemore` (bin "learnrustsomemore") due to 1 previous error
```
[Update from 2024-11-17: This is due to the first example of `let var_x = "My string";` having a value of `&str`, which is Copy. The second example uses the `.to_string()` method, resulting in a value of the owned type `String`, which is not Copy.]
## 2024-11-03
Who knew working with strings could be this complicated? Lol.
## 2024-11-17
[This code has way too many comments and is presented regardless.]
``` rust
fn main() { // Start of the main function.
let mut x = vec![1, 2, 3]; // Declare a mutable vector of i32 values.
for num in &mut x { // Create a for loop which borrows a mutable
// reference to our vector x.
*num += 1; // For each dereferenced item in x, increment it by 1.
} // Ending of our for loop's scope.
println!("{:?}", x); // Print our results.
} // Ending of the main function.
```