Control Flow

if

func main() {
  let x = 5;
  if x < 5 { // condition must be type of boolean
    println!("condition true");
  } else {
    println!("condition false");
  }
}

Rust will not automatically try to convert non-Boolean types to a Boolean. You must be explicit and always provide if with a Boolean as its condition.

• 너무 많은 else if 는 Rust에서 좋은 방법이 아니다.
• match 를 사용하는게 좋을 수도 있다.

fn main() {
    let condition = true;
    let number = if condition {
        5
    } else {
        6
    };

    println!("The value of number is: {}", number);
}

• let statement에서 if 문으로 값을 초기화 할 수 있다.

• The values that have the potential to be results from each arm of the if must be the same type.

loops

loop, while, for

fn main() {
  let mut counter = 0;

  // you can add the value you want returned after the break expression you use to stop the loop;
  // that value will be returned out of the loop so you can use it, as shown here:
  let result = loop {
    counter += 1;
    if counter == 10 {
      break counter * 2; // will be returned
    }
  };
  
  loop {
    println!("again!");
  }
      
}

fn main() {
    let a = [10, 20, 30, 40, 50];
    let mut index = 0;

    while index < 5 {
        println!("the value is: {}", a[index]);

        index += 1;
    }
}
// 위 코드는 while로 하는 것보다는 for로 하는 것이 훨씬 좋은 방법이다.
// 속도도 빠르고, error 발생(index err) 방지
fn main() {
    let a = [10, 20, 30, 40, 50];

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

The safety and conciseness of for loops make them the most commonly used loop construct in Rust. Even in situations in which you want to run some code a certain number of times, most Rustaceans would use a for loop.

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