如何拿返回值，如何不传递所有权就更改原值？如果想操作更改元变量要怎么做呢？

分别执行以下go代码：

func main() {var a = 10//calc1(a)//a = calc_return(a)calc2(&a)a = 100calc3(&a)fmt.Println(a)
}
func calc1(num int) {num += num
}
func calc_return(num int) int {num += numreturn num
}
func calc2(num *int) {*num += *num
}
func calc3(num *int) {*num += *num
}

rust代码：

use std::string;
fn main() {let mut s1  = String::from("learn rust");s1 =  foo_return(s1);println!{"{s1}"};  }
fn  foo_return(s:String)->String{println!{"{s}"};s
}

use std::string;
fn main() {let mut s1  = String::from("learn rust");// foo1(s1);// foo2(&s1);foo3(&mut s1);println!{"{s1}"};foo3(&mut s1);}
fn  foo1(s:String){println!{"{s}"};
}
fn  foo2(s:&String){println!{"{s}"};
}
fn  foo3(s:&mut String){s.push_str(",you can be 666");println!{"{s}"};
}

自己去体会其中的不同之处