let
关键字fn main() {
let mut x = 5;
println!("x = {}", x); //5 可变
x = 6;
println!("x = {}", x); //6 可变
let x = 7;
println!("x = {}", x); //7 不可变
}
const MAX_POINTS:u32 = 100_000;
const MAX_POINTS:u32 = 100_000;
fn main() {
const MAX_POINTS:u32 = 100_000;
}
fn main() {
let x = 5;
let x = x + 1; //6
let x = x * 2; //12
println!("x is {}", x); //12
}
fn main() {
let spaces = " "; //4个空格 $str
let spaces = spaces.len(); //4 usize
println!("spaces is {}", spaces); //4
}