fn main(){
  let age: u32 = 17;
  if age > 18{
    println!("You are an adult");
  }
}

fn main(){
  let age: u32 = 17
  if age>18{
    println!("You are an adult");
  }else{
    println!("You are not an adult");
  }
}

fn main(){
  let number = 92;
  if number % 9 == 0{
    println!("number is divisible by 9");
  } else if number % 5 == 0{
    println!("number is divisible by 5");
  }else if number % 3 == 0{
    println!("number is divisible by 3");
  }else{
    println!("number is not divisible by 9, 5, 3");
  }
}

Loops 环

Loops are used to go over through a block of code till explicitly specified to stop or if a certain condition is met.
循环用于遍历代码块，直到明确指定停止或满足特定条件。

loop keyword  loop 关键字

The loop keyword tells rust to run a block of code till told to stop using the break keyword
loop关键字告诉rust运行一段代码，直到停止使用 break 关键字

fn main() {
    let mut i: u32 = 0;
    let mut j: i32 = 10;

  // labelled infinite loop with break statements
    'counting_down: loop {
        if j >= 0 {
            println!("{}", j);
            j -= 1;
        } else {
            println!("counting down loop complete");
            break 'counting_down;
        }
    }
}

Explanation: 说明：

• The main function is the entry point of the Rust program.
  main 函数是Rust程序的入口点。
• j of type i32 (signed 32-bit integer) initialized with the value 10.
  类型 i32 （有符号32位整数）的 j ，初始化为值10。
• The code enters a labeled infinite loop marked with the label 'counting_down.
  代码进入一个标记为 'counting_down 的带标签的无限循环。
• Inside the loop, there’s a conditional statement checking if j is greater than or equal to 0.
  在循环内部，有一个条件语句检查 j 是否大于或等于0。
• If true, it prints the current value of j using println! and decrements j by 1.
  如果为true，则使用 println! 打印 j 的当前值，并将 j 递减1。
• If false (when j is less than 0), it prints a message and breaks out of the loop labeled 'counting_down.
  如果为false（当 j 小于0时），它将打印一条消息并跳出标记为 'counting_down 的循环。
• The loop continues indefinitely until the break 'counting_down; statement is executed.
  循环将无限期地继续，直到执行 break 'counting_down; 语句。
• The label 'counting_down is used to specify which loop to break out of, especially when dealing with nested loops.
  标签 'counting_down 用于指定要中断哪个循环，特别是在处理嵌套循环时。

While loops While循环

A while loop repeatedly executes a block of code as long as a specified condition is true.
只要指定的条件为真， while 循环就会重复执行代码块。

Example: 范例：

fn main(){
  let mut num: u8 = 4;
  while num!=0 {
    println!("{}",num);
    num-=1;
  }
}

Explanation: 说明：

• A mutable variable num is declared and initialized with the value 4. It has the type u8 (unsigned 8-bit integer).
  声明了一个可变变量 num ，并使用值4进行初始化。它的类型为 u8 （无符号8位整数）。
• The code enters a while loop with the condition num != 0.
  代码进入一个带有条件 num != 0 的 while 循环。
• Inside the loop, it prints the current value of num using println!.
  在循环内部，它使用 println! 打印 num 的当前值。
• It then decrements the value of num by 1 with the num -= 1; statement.
  然后使用 num -= 1; 语句将 num 的值减1。
• The loop continues as long as the condition num != 0 is true.
  只要条件 num != 0 为真，循环就会继续。
• The program prints the values of num in descending order from its initial value (4) until it becomes 0.
  程序按从初始值（4）到0的降序打印 num 的值。
• Once num becomes 0, the loop exits, and the program continues to any subsequent code outside the loop.
  一旦 num 变为0，循环退出，程序继续执行循环外的任何后续代码。

For Loops for循环

A for loop iterates over a range, collection, or iterator, executing a block of code for each iteration.
for 循环遍历范围、集合或迭代器，每次迭代执行一个代码块。

Examples: 示例如下：

fn main(){
  //for loops in arrays
  let array: [u8; 10] = [10, 20, 30, 40, 50, 60, 70, 80, 90, 100];
  println!("For loop to access array");
    for item in array {
        println!("{}", item);
    }

  //for loops in ranges
  println!("For loops in range ");
    for number in 0..=5 {
        println!("{number}");
    }
  println!("For loops in range (reversed)");
    for number in (0..=5).rev() {
        println!("{number}");
    }
}