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Rust 101

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Rust 入门

起步​

创建文件 main.rs，内容如下：

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

编译代码：

$ rustc main.rs

$ ls
main  main.rs

运行代码：

$ ./main

# Windows
$ .\main.exe

工具​

Cargo​

# 创建项目
$ cargo new <project_name>

# 编译项目
$ cargo build

# 编译并运行项目
$ cargo run

# 检查项目
$ cargo check

rustfmt​

$ rustfmt main.rs

变量​

修改变量：

fn main() {
    let mut x = 4;
    println!("x = {}", x); // x = 4
    x = 5;
    println!("x = {}", x); // x = 5
}

重定义变量：

fn main() {
    let x = 4;
    println!("x = {}", x); // x = 4
    let x = 5;
    println!("x = {}", x); // x = 5
}

❌ 不能修改变量类型：

fn main() {
    let mut x = 4;
    println!("x = {}", x); // x = 4
    x = "hello"; // expected integer, found `&str`
    println!("x = {}", x);
}

✅ 可以重定义变量类型：

fn main() {
    let x = 4;
    println!("x = {}", x); // x = 4
    let x = "hello";
    println!("x = {}", x); // x = hello
}

常量：

fn main() {
    const INTERVAL: u32 = 1000;
    println!("INTERVAL = {}", INTERVAL); // INTERVAL = 1000

    const INTERVAL: u32 = 3000; // ❌ 不能重定义常量
}

数据类型​

fn main() {
    // Scalar Types
    let a = 4; // 默认为i32
    let b: i8 = 4; // i8, i16, i32, i64, i128
    let c: u8 = 4; // u8, u16, u32, u64, u128
    // u32: 0 ~ 2^32-1
    // i32: -2^16 ~ 2^16-1

    let d = 4.0; // 默认为f64
    // f32单精度; f64双精度

    let e: bool = true; // bool: true, false

    let f: char = 'a'; // char 注意这里的单引号

    // Compound Types
    // Tuple
    let g: (i32, f64, u8) = (500, 6.4, 1); // (i32, f64, u8)
    let (m, n, o) = g; // 500, 6.4, 1
    // g.0

    // Array
    let h = [1, 2, 3, 4, 5]; // [i32; 5]
    let i: [i32; 5] = [1; 5]; // [1, 1, 1, 1, 1]
    // h[0]
}

输入和输出​

use std::io;

fn main() {
    let mut input = String::new();

    io::stdin()
        .read_line(&mut input)
        .expect("Failed to read line");

    println!("{}", input);
}

类型转换​

fn main() {
    let x: u8 = 8; // 0 - 255
    let y: i8 = 10; // -128 - 127
    let z = x + y; // error

    let x = 8.0f32;
    let y = 10.0f32;
    let z = x / y; // 0.8

    let x = 8_000_i64;
    let y = 10_i64;
    let z = x / y; // 800

    let x = 8_000_i64;
    let y = 10_i32;
    let z = x / (y as i64); // 800

    let mut input = String::new();
    io::stdin()
        .read_line(&mut input)
        .expect("Failed to read line");

    println!("{}", input);

    let int_input: i64 = input.trim().parse().unwrap();
    println!("{}", int_input + 2);
}

条件与流程控制​

fn main() {
    // < > <= >= == !=
    // && || !
    // if / else if / else

    // let cond = 2 < 3.2; // error

    let cond = (2 as f64) < 3.2;
    if cond {
        println!("2 < 3");
    } else if (2 as f64) == 3.2 {
        println!("2 == 3");
    } else {
        println!("2 > 3");
    }
    println!("Hello, world!");
}

表达式和声明​

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

    let result = add_numbers(1, 2);
    println!("The value of result is: {}", result);

    let num = {
        let x = 1;
        x + 1 // 没有分号，这是一个表达式
    };
    println!("The value of num is: {}", num);
}

fn add_numbers(x: i32, y: i32) -> i32 {
    return x + y;
}

参考资料​