rust/hello_world/src/main.rs

// 文件名随意，入口main函数，
// 编译： rustc main.rs
// 运行1： cargo run --package rust-quickstart --bin rust-quickstart
// 运行2：./main

fn main() {
    println!("Hello, world!");

    // 不可变变量
    let a: i32 = 2;

    // 可变变量
    let mut b = 123;
    b = 456;
    println!(" a is {}, a again is {}", a, a);

    // let 重载
    let x = 5;
    let x = x + 1;
    let x = x * 2;
    println!("The value of x is: {}", x);

    // 数学运算
    let _sum = 5 + 10; // 加
    let _difference = 95.5 - 4.3; // 减
    let _product = 4 * 30; // 乘
    let _quotient = 56.7 / 32.2; // 除
    let _remainder = 43 % 5; // 求余

    let _arr_a: [i32; 6] = [1, 2, 3, 3, 4, 5];

    let number = 3;
    if number < 5 {
        println!("less than 5");
    } else {
        println!("more than 5");
    }

    while number != 4 {
        println!("number is : {}", number);
    }

    let mut i = 0;
    while i < 10 {
        i += 1;
        println!("i is {}", i);
    }

    for i in _arr_a.iter() {
        println!("值为：{}", i);
    }

    // 无限循环 while(true)
    // loop {

    // }

    // 切片
    let s = String::from("broadcast");

    let part1 = &s[0..5];
    let part2 = &s[5..9];

    println!("{}={}+{}", s, part1, part2);
}