let some_number = Some(5); let absent_number: Option<i32> = None; // You cannot add Option<i32> to i32 directly. let x: i32 = 5; let y: Option<i32> = Some(10); // let sum = x + y; // ERROR: mismatched types
let s = String::from("hello world"); let hello = &s[0..5]; // type: &str let world = &s[6..11]; String literals are &str (immutable slices). struct User active: bool, username: String, sign_in_count: u64, ultimate rust crash course
By the end of this article, you will read and write basic Rust, understand ownership, and be ready to tackle real projects. Most bugs come from memory errors (use-after-free, dangling pointers, data races) or concurrency issues. Languages like C/C++ give you speed but no safety. Languages like Java/Go give you safety but with a garbage collector (GC) that adds runtime overhead. Most bugs come from memory errors (use-after-free, dangling
fn read_username_from_file() -> Result<String, io::Error> let mut s = String::new(); File::open("hello.txt")?.read_to_string(&mut s)?; Ok(s) fn read_username_from_file() ->
, ;
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