Introducing Rust
Why use Rust for the guide?
Say you've decided you want to eat 35 burgers. Python is the friend that helps you order them to be delivered at your door. C++ is the friend who says 'do whatever you want'. Rust is the friend who stops you and then recommends you a salad. That may be annoying at times, especially if you were just craving 35 entire burgers, but it is what is best for you. Since the guide is not a beginners introduction to programming, and I will occasionally introduce advanced concepts, having a language that keeps you on the straight and narrow, even if it seems pedantic and like it is getting in your way, is a genuine advantage. If the Rust compiler accepts your code without any unsafe sections, it is probably going to work.
Another point in Rust's favor was the easy setup and use on Windows, Linux and macOS.
The setup time needed to be less than 10 minutes and the chosen language needed an
easy-to-use, preferably integrated, package manager which didn't cause too many versioning issues.
The options considered were C, C++ and Rust. C and C++ contained too few guardrails and required the
use of an external package manager, as well as the use of header files and build systems.
Rust takes care of all that with cargo.
cargo can help you run and test your code, as well as helping downloading and building all of the
dependencies in the Cargo.toml file, which you will find in the root of each code project.
Rust's very helpful compiler is likely to be a boon for guiding users towards sensible code.
The process of having to program in such a memory focused, modern, compiled language
will turn what is otherwise an implicit, unspoken process inside out,
forcing you to think about what good code is, where is the data located in memory,
which thread has access to which data, and so on.
Setup
To use the code in the course, as well as doing the exercises, first of all, you should have git and Rust installed.
Once you have installed both, ensure they are properly installed by calling git --version and
cargo --version in your terminal of choice. Your Rust version should be at least 1.68.
At the least, the code in the guide won't function without support for the 2021 or newer version of Rust.
- git clone the guides repository
git clone https://github.com/absorensen/the-guide.git - In your terminal navigate into the folder that just appeared
- Navigate to
m0_introduction::code::is_my_system_ready - In the command line write
cargo run. This might take a while as cargo will now download and build some dependencies, and then compile and run the code in debug mode. - For IDE, the guide has been developed with VS Code with the extensions rust-analyzer, CodeLLDB, Rust Syntax, WGSL, wgsl-analyzer and optionally Dracula For Rust Theme.
Projects
Projects are how a Rust codebase is organized. A project can contain subprojects, but the guide won't use this.
Navigating to your terminal and writing cargo new my_project will create a project with a Cargo.toml
file and directory named src in the root. Inside the src directory there will be a file
named main.rs. The Cargo.toml is a file describing the name of your project and its dependencies,
which will be empty to begin with. But if you write some dependencies, next time you build the code with
cargo build or cargo run, with or without the --release flag, cargo will download and build all
of the dependencies. By default cargo will look in the src directory for your code. All of the files with the
.rs suffix are Rust source files.
Entering cargo run will compile and run your code in debug mode, which means it will be easier to step
through the code and you will get better error messages. It will also result in significantly less compilation
time, but slower run time. If you add cargo run --release it will compile in release mode.
Compilation will take longer, the code will run faster, but debugging will be harder.
To save on space, especially for some of the smaller projects where you just need to run a command or two,
write cargo clean once you are done to remove all of the relevant dependencies.
Testing
Cargo can also handle unit testing of code. It requires that the project is split into an application and a library part, allowing the test to just test the library. In practice, what is usually recommended is to just have a very small function in your application which tells your library to start running your code.
Navigate to the project at m0_introduction::code::how_to_test to see how a typical project is
setup. Try running the commands cargo run, followed by cargo test. See how the code ran with
cargo run, but cargo test actually told you which functions weren't living up to expectations?
Setting up these unit tests is also how the guide tells you that the code you have been asked to write is correct.
When doing exercises, keep going until all of the tests pass!
Now be sure to take a minute to look at the files involved in a project and read all of the comments! Sometimes you need more info as to what went wrong with the test. There's a fix for that on Windows.
On some computers the GPU tests will currently fail unless being run with cargo test -- --test-threads=1
as the tests are running concurrently. All of the tests requiring GPU access will try to grab the GPU without
sharing resources. Even then it might fail. You can just try a few more times or try to run tests individually.
Clippy
Clippy is cargo's tool for giving suggestions for improving
your code and making it more akin to idiomatic Rust. The guide has most code conformant to Clippy's suggestions,
however I choose to diverge to make the code simpler and easier to understand for people who have
never programmed Rust. Clippy's messages are very informative and a good learning experience.
It is recommended that you use Clippy in your own code. It is as simple as calling cargo clippy.
Running it on the how_to_test project, Clippy returns the following message -
rustfmt
rustfmt is a formatter for Rust. Surprise!
You can install it by running rustup component add rustfmt in a terminal. From then on you can run commands
like cargo fmt, which automatically changes the code in your current crate (subproject,
or the entire project if you are standing in the root).
fix
fix is a tool for taking as many of those pesky compiler warnings as possible, and fixing your code for you.
You just enter cargo fix.