formatted-output

[giscus[bot]]

formatted-output

Learning Rust By Practice, narrowing the gap between beginner and skilled-dev with challenging examples, exercises and projects.

https://zh.practice.rs/formatted-output.html

[ssieie]

done

[Ghy0202]

1、format的参数顺序

/* 填空 */
fn main() {
    println!("{0}, this is {1}. {1}, this is {0}", "Alice", "Bob");// => Alice, this is Bob. Bob, this is Alice
    assert_eq!(format!("{1}{0}", 2,1), "12");
    assert_eq!(format!("{1}{0}{}{}", 1, 2), "2112");
    println!("Success!");
}

2、具体参数名

fn main() {
    println!("{argument}", argument = "test"); // => "test"

    /* 填空 */
    assert_eq!(format!("{name}{}", 1, name=2), "21");
    assert_eq!(format!("{a} {c} {b}",a = "a", b = 'b', c = 3 ), "a 3 b");
    
    /* 修复错误 */
    // 具名参数必须放在其它参数后面
    println!("{abc}{}", 2,abc = "def");

    println!("Success!")
}

3、字符串对齐

fn main() {
    // 下面两个都是通过 5 个空格来填充
    println!("Hello {:5}!", "x"); // =>  "Hello x    !"  
    println!("Hello {:1$}!", "x", 5); // =>  "Hello x    !"

    /* 填空 */
    assert_eq!(format!("Hello {1:0$}!", 5, "x"), "Hello x    !");
    assert_eq!(format!("Hello {:width$}!", "x", width = 5), "Hello x    !");

    println!("Success!")
}

4、左对齐、右对齐以及使用指定的字符填充给对齐

fn main() {
    // 左对齐
    println!("Hello {:<5}!", "x"); // => Hello x    !
    // 右对齐
    assert_eq!(format!("Hello {:>5}!", "x"), "Hello     x!");
    // 居中对齐
    assert_eq!(format!("Hello {:^5}!", "x"), "Hello   x  !");

    // 左对齐，并使用 `&` 填充
    assert_eq!(format!("Hello {:&<5}!", "x"), "Hello x&&&&!");

    println!("Success!")
}

5、用0来填充数字

fn main() {
    println!("Hello {:5}!", 5); // => Hello     5!
    println!("Hello {:+}!", 5); // =>  Hello +5!
    println!("Hello {:05}!", 5); // => Hello 00005!
    println!("Hello {:05}!", -5); // => Hello -0005!

    /* 填空 */
    assert!(format!("{number:0>width$}", number=1, width=6) == "000001");
    
    println!("Success!")
}

6、浮点数精读

/* 填空 */
fn main() {
    let v = 3.1415926;

    println!("{:.1$}", v, 4); // same as {:.4} => 3.1416 

    assert_eq!(format!("{:.2}", v), "3.14");
    assert_eq!(format!("{:+.2}", v), "+3.14");
    assert_eq!(format!("{:.0}", v), "3");

    println!("Success!")
}

7、字符串长度

fn main() {
    let s = "Hello, world!";

    println!("{0:.5}", s); // => Hello

    assert_eq!(format!("Hello {1:.0$}!", 3, "abcdefg"), "Hello abc!");

    println!("Success!")
}

8、进制转换

fn main() {
    assert_eq!(format!("{:#b}", 27), "0b11011");
    assert_eq!(format!("{:#o}", 27), "0o33");
    assert_eq!(format!("{:#x}", 27), "0x1b");
    assert_eq!(format!("{:#X}", 27), "0x1B");

    println!("{:x}!", 27); // 没有前缀的十六进制 => 1b

    println!("{:#010b}", 27); // 使用 0 来填充二进制，宽度为 10 => 0b00011011

    println!("Success!")
}

9、

fn get_person() -> String {
    String::from("sunface")
}

fn get_format() -> (usize, usize) {
    (4, 1)
}


fn main() {
    let person = get_person();
    println!("Hello, {person}!");

    let (width, precision) = get_format();
    let scores = [("sunface", 99.12), ("jack", 60.34)];
    /* 让下面的代码输出:
    sunface: 99.1
    jack: 60.3
    */
    for (name, score) in scores {
        println!("{name}: {score:.1}");//或者： println!("{name}: {score:width$.precision$}");
    }
}

[tjw123hh]

{:e}和{:E}都可以使用.+数字指定底数的精度
{:p}只有参数为*const {integer}时才可使用

[TableBear]

done

[LovingElysia]

基础部分完结撒花，感谢分享知识

[Icemans007]

下面的 :2e/E 前面数字是什么意思？我得到的结果没区别

println!("{:3e}", 1111000001);   // 1.111000001e9
println!("{:2E}", 1111000001);   // 1.111000001E9