跨出界

var code = 123; // In older specifications, only the var keyword is required for declaration
let firstName = "kaby"; // After ES6, let represents a variable that can be modified
const lastName = "Zhao"; // After ES6, const represents a constant that cannot be modified

firstName = "bike"; // Normal
lastName = "Hu"; // Error - Uncaught TypeError: Assignment to constant variable

// By default, all variables in Rust are not allowed to be modified, such as
let code = 123; 
println!("The value of code is: {code}"); // Normal
code = 456; // Error - cannot assign twice to immutable variable `code`

// Declare a mutable variable
let mut name = "lulu";
println!("The name is: {name}"); // Output lulu
name = "jack";
println!("The name is: {name}"); // Output jack

// The same keywords can be used to declare constants
// Constants cannot be used with mut
// Constants cannot be changed by default
const WAIT_SEC:u32 = 30;

// Variable shadowing
fn main() {
    let x = 5;
    let x = x + 1;
    {
        let x = x * 2;
				// 12
        println!("The value of x in the inner scope is: {x}");
    }
		// 6
    println!("The value of x is: {x}");
}

// Function declaration
function getName() {
	return "jack";
}

// Using variables
let getInfo = function() {
	return {
		"age": 18
	}
}

// The above can also be expressed using arrows
let getInfo = () => ({ "age": 18 })

// Logic
// Conditional statements if / switch
if (getName() == "jack") {
	return "lose";
} else if (getName() == "lose") {
	return "moth";
} else {
	return "";
}

// Loops for...in / for...of / while
let arr = [1, 2, 3];
for(let i = 0; i < arr.length; i++) {
	console.info(i);
}

// As JavaScript is a weakly typed language, it automatically infers and converts variable types
// So for some comparisons and judgments, it is relatively simple, just use == directly
// However, unexpected situations may also occur, such as
// "5" == 5 evaluates to true, so you need to be careful and use "5" === 5 to solve it.
// You can also directly compare strings for equality
// "abc" == "cde"

// Functions
fn main() {
    println!("hello world");

    another_function();

    // print_labeled_measurement
    print_labeled_measurement(5, 'h');

    // plus_one
    let po = plus_one(8);
    // po == 9
    println!("The result of the calculation is {}", po);

    // do logic_info function
    logic_info("abc", 12);

    // loop
    loop_info();
}

// another_function
fn another_function() {
    println!("another_function");
}

// Function with parameters
fn print_labeled_measurement(value: i32, unit_label: char) {
    println!("The measurement is: {value}{unit_label}");
}

// If a function has a return value, you also need to define the return type
fn plus_one(x: i32) -> i32 {
    return x + 1;
}

// Logic
fn logic_info(name: &str, age: i32) {
    println!("{}'s age is {}", name, age);

    // For numeric types, you can use if for comparison directly
    if age > 12 {
        println!("Over 12 years old, need to buy a ticket");
    } else if age < 12 {
        println!("Ride for free");
    } else {
        println!("12 years old, need to buy a ticket");
    }

    // String comparison
    if name == "lulu" {
        println!("Hello, {}", name);
    } else {
         println!("Name does not match");
    }
}

// Loops
fn loop_info() {
    // while loop
    let mut number = 3;
    while number != 0 {
        println!("{number}!");
        number -= 1;
    }
    println!("LIFTOFF!!!");

    // for loop
    let a = [10, 20, 30, 40, 50];
    for element in a {
        println!("the value is: {element}");
    }

    // loop loop
    // Note that the loop loop does not automatically terminate, you need to manually break
    let mut counter = 0;
    let result = loop {
        counter += 1;
        if counter == 10 {
            break counter * 2;
        }
    };
    println!("The result of the loop loop is: {result}");
}

// You can view the specific code here
// https://play.rust-lang.org/?gist=e87ef95f861dbc22bf8f23722e40aa34