Rust 代码片段：生成随机数据

原文：https://rust-lang-nursery.github.io/rust-cookbook/algorithms/randomness.html

随机数字

use rand::Rng;

fn main() {
    letmut rng = rand::thread_rng();

    let n1: u8 = rng.gen();
    let n2: u16 = rng.gen();
    println!("Random u8: {}", n1);
    println!("Random u16: {}", n2);
    println!("Random u32: {}", rng.gen::<u32>());
    println!("Random i32: {}", rng.gen::<i32>());
    println!("Random float: {}", rng.gen::<f64>());
}

一定范围内的随机数

use rand::Rng;

fn main() {
    letmut rng = rand::thread_rng();
    println!("Integer: {}", rng.gen_range(0..10));
    println!("Float: {}", rng.gen_range(0.0..10.0));
}

下面这种在重复生成某一范围内的随机数方面效果一样，但速度更快。

use rand::distributions::{Distribution, Uniform};

fn main() {
    letmut rng = rand::thread_rng();
    let die = Uniform::from(1..7);

    loop {
        let throw = die.sample(&mut rng);
        println!("Roll the die: {}", throw);
        if throw == 6 {
            break;
        }
    }
}

用给定的分布生成随机数

use rand_distr::{Distribution, Normal, NormalError};
use rand::thread_rng;

fn main() -> Result<(), NormalError> {
    letmut rng = thread_rng();
    let normal = Normal::new(2.0, 3.0)?;
    let v = normal.sample(&mut rng);
    println!("{} is from a N(2, 9) distribution", v);
    Ok(())
}

用指定类型生成随机值

use rand::Rng;
use rand::distributions::{Distribution, Standard};

#[derive(Debug)]struct Point {
    x: i32,
    y: i32,
}

impl Distribution<Point> for Standard {
    fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> Point {
        let (rand_x, rand_y) = rng.gen();
        Point {
            x: rand_x,
            y: rand_y,
        }
    }
}

fn main() {
    letmut rng = rand::thread_rng();
    let rand_tuple = rng.gen::<(i32, bool, f64)>();
    let rand_point: Point = rng.gen();
    println!("Random tuple: {:?}", rand_tuple);
    println!("Random Point: {:?}", rand_point);
}

用字母表生成随机密码

use rand::{thread_rng, Rng};
use rand::distributions::Alphanumeric;

fn main() {
    let rand_string: String = thread_rng()
        .sample_iter(&Alphanumeric)
        .take(30)
        .map(char::from)
        .collect();

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

用自定义字符范围生成随机密码

fn main() {
    use rand::Rng;
    const CHARSET: &[u8] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZ\
                            abcdefghijklmnopqrstuvwxyz\
                            0123456789)(*&^%$#@!~";
    const PASSWORD_LEN: usize = 30;
    letmut rng = rand::thread_rng();

    let password: String = (0..PASSWORD_LEN)
        .map(|_| {
            let idx = rng.gen_range(0..CHARSET.len());
            CHARSET[idx] aschar
        })
        .collect();

    println!("{:?}", password);
}