How to Read Rust Code Quickly?

Question (Prompt):

Show me a Rust code example using the following keywords: trait, struct, where, fn, impl, for, use, derive. And teach me how to understand and read it quickly.

Response (GPT-4):

Sure, here's an example of a Rust code snippet using the keywords you listed:

use std::fmt::Display;

struct Rectangle {
    width: u32,
    height: u32,

struct Circle {
    radius: u32,

trait Area {
    fn area(&self) -> u32;

impl Area for Rectangle {
    fn area(&self) -> u32 {
        self.width * self.height

impl Area for Circle {
    fn area(&self) -> u32 {
        3 * self.radius * self.radius

fn print_area<T: Area + Display>(shape: T) {
    println!("The area is: {}", shape.area());

Now, let's break it down.

  • use std::fmt::Display; This line is importing the Display trait from the fmt module which is part of the standard library. The Display trait is used for formatting with {}.

  • #[derive(Debug)] This is an attribute applied to the structs Rectangle and Circle. It automatically generates an implementation of the Debug trait, which allows easy debugging output for these structs.

  • struct Rectangle and struct Circle These are two simple struct declarations. Rectangle has two fields, width and height, both of type u32 (32-bit unsigned integers). Circle has one field, radius, also of type u32.

  • trait Area This is a trait definition for Area. Traits define shared behavior that structs (or enums) can implement. In this case, anything that wants to implement Area must provide a function area that takes &self (a reference to the instance) and returns a u32.

  • impl Area for Rectangle and impl Area for Circle These are the implementations of the Area trait for the Rectangle and Circle structs. They provide the behavior for the area method as defined in the Area trait.

  • fn print_area<T: Area + Display>(shape: T) This is a generic function print_area which takes an argument shape of any type T that implements both Area and Display traits. It then prints the area of the shape.

Please note that the Display trait isn't implemented in the structs in the provided code which might lead to a compile error. The Display trait is just used for demonstration purposes of the use keyword.

This is a basic overview of how these keywords work in Rust. There's a lot more depth to each of them, especially when you get into more complex code. Let me know if you have any other questions!

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