例子1：

原题

fn main() {
    call_me();
}

修改后：

fn call_me() {

}

fn main() {
    call_me();
}

这里添加了一个函数定义，我们看下结果

例子2:

fn main() {
    call_me(3);
}

fn call_me(num:) {
    for i in 0..num {
        println!("Ring! Call number {}", i + 1);
    }
}

修改后：

fn main() {
    call_me(3);
}

fn call_me(num:i32) {
    for i in 0..num {
        println!("Ring! Call number {}", i + 1);
    }
}

例子3：

原题：

fn main() {
    call_me();
}

fn call_me(num: u32) {
    for i in 0..num {
        println!("Ring! Call number {}", i + 1);
    }
}

修改后：

fn main() {
    call_me(2);
}

fn call_me(num: u32) {
    for i in 0..num {
        println!("Ring! Call number {}", i + 1);
    }
}

例子4：

原题：

fn main() {
    let original_price = 51;
    println!("Your sale price is {}", sale_price(original_price));
}

fn sale_price(price: i32) -> {
    if is_even(price) {
        price - 10
    } else {
        price - 3
    }
}

fn is_even(num: i32) -> bool {
    num % 2 == 0
}

修改后：

fn main() {
    let original_price = 51;
    println!("Your sale price is {}", sale_price(original_price));
}

fn sale_price(price: i32) -> i32 {
    if is_even(price) {
        price - 10
    } else {
        price - 3
    }
}

fn is_even(num: i32) -> bool {
    num % 2 == 0
}

例子5：

原题：

fn main() {
    let answer = square(3);
    println!("The answer is {}", answer);
}

fn square(num: i32) -> i32 {
    num * num;
}

修改后：

fn main() {
    let answer = square(3);
    println!("The answer is {}", answer);
}

fn square(num: i32) -> i32 {
    num * num
}