How do closures work in Rust and what are the capture modes?

Closures are anonymous functions: • Can capture environment variables • Three capture modes: by reference, by mutable reference, by value • Implement Fn, FnMut, or FnOnce traits • Type inference for parameters • Move keyword for ownership transfer Example: let x = 4; let equal_to_x = |z| z == x; // captures x by reference let mut list = vec![1, 2, 3]; let mut borrows_mutably = || list.push(7); // captures by mutable reference let moves = move || println!("x: {}", x); // moves x into closure