Using Crates from crates.io

fn main() {
    println!("crates.io hosts community packages like serde, rand, and clap");
}

[dependencies]
rand = "0.8"

cargo add rand

fn main() {
    println!("This course sticks to the standard library so every example can run offline");
}

1. Assuming a crate is added to your project automatically just by writing use in your code -- it must be declared in Cargo.toml first.
2. Adding a crate without checking its version compatibility, which can pull in breaking changes unexpectedly.
3. Forgetting Judge0-style sandboxes without network access cannot download crates, so exercises there must rely on the standard library only.

• crates.io is the official public registry for Rust packages (crates).
• Adding a crate as a [dependencies] entry in Cargo.toml makes it available to use in your code.
• cargo add crate_name is a convenient way to add a dependency without manually editing Cargo.toml.
• Popular crates like serde (serialization) and rand (random numbers) extend what the standard library alone can do.