rust_book_code 0.2.1

pub fn if_else() {
    let number = 3;

    if number < 5 {
        println!("condition was true");
    } else {
        println!("condition was false");
    }

    if_else_if();

    if_expression();
}

fn if_expression() {
    let condition = true;
    // if 的每个分支的可能的返回值都必须是相同类型
    let number = if condition { 5 } else { 6 };
    println!("The value of number is: {number}");
}

fn if_else_if() {
    let number = 6;

    if number % 4 == 0 {
        println!("number is divisible by 4");
    } else if number % 3 == 0 {
        println!("number is divisible by 3");
    } else if number % 2 == 0 {
        println!("number is divisible by 2");
    } else {
        println!("number is not divisible by 4, 3, or 2");
    }
}

pub fn loop_func() {
    // 无限循环
    // loop {
    //     println!("again!");
    // }

    let mut counter = 0;

    let result = loop {
        counter += 1;

        if counter == 10 {
            break counter * 2;
        }
    };

    println!("The result is {result}");
}

pub fn loop_label() {
    let mut count = 0;
    'counting_up: loop {
        println!("count = {count}");
        let mut remaining = 10;

        loop {
            println!("remaining = {remaining}");
            if remaining == 9 {
                break;
            }
            if count == 2 {
                break 'counting_up;
            }
            remaining -= 1;
        }

        count += 1;
    }
    println!("End count = {count}");
}

pub fn while_func() {
    let mut number = 3;
    while number != 0 {
        println!("{number}!");

        number -= 1;
    }
    println!("LIFTOFF!!!");
}

fn while_element() {
    let a = [10, 20, 30, 40, 50];
    let mut index = 0;
    while index < 5 {
        println!("the value is: {}", a[index]);
        index += 1;
    }
}

pub fn for_element() {
    // while_element();

    let a = [10, 20, 30, 40, 50];

    for element in a {
        println!("the value is: {element}");
    }

    for_rev();
}

fn for_rev() {
    for number in (1..4).rev() {
        println!("{number}!")
    }
    println!("LIFTOFF!!")
}