Structs: Custom Data Groupings

Structs are the primary compound types in Rust used to model domain objects. Rust supports three distinct struct layouts:

1. Named-Field Structs

The standard struct form where each field has an explicit name and type. Useful for complex models.

struct KeyCoordinates {
    x: i32,
    y: i32,
}

let pt = KeyCoordinates { x: 100, y: 200 };

2. Tuple Structs

Fields do not have names; they are accessed by 0-based indices. Ideal for lightweight type wrappers.

struct Keystroke(u32, bool); // key_code, is_down

let event = Keystroke(0x41, true);
let key = event.0;

3. Unit Structs

Fields are omitted entirely. Used to implement traits on marker types without storing data.

struct GlobalListener;

Performance Metrics

• Storage Cost: Packed contiguously in memory on the stack.
• Access speed: Compile-time offsets mean zero-runtime field access costs.