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< main >
< h1 id = "生成随机值" > < a class = "header" href = "#生成随机值" > 生成随机值< / a > < / h1 >
< h3 id = "生成随机数" > < a class = "header" href = "#生成随机数" > 生成随机数< / a > < / h3 >
< p > 使用 < a href = "https://docs.rs/rand/*/rand/fn.thread_rng.html" > rand::thread_rng< / a > 可以获取一个随机数生成器 < a href = "https://docs.rs/rand/0.8.5/rand/trait.Rng.html" > rand::Rng< / a > ，该生成器需要在每个线程都初始化一个。< / p >
< p > 整数的随机分布范围等于类型的取值范围，但是浮点数只分布在 < code > [0, 1)< / code > 区间内。< / p >
< pre > < pre class = "playground" > < code class = "language-rust editable edition2021" > use rand::Rng;
fn main() {
let mut 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> ());
}
< / code > < / pre > < / pre >
< h3 id = "指定范围生成随机数" > < a class = "header" href = "#指定范围生成随机数" > 指定范围生成随机数< / a > < / h3 >
< p > 使用 < a href = "https://rust-lang-nursery.github.io/rust-cookbook/algorithms/randomness.html" > Rng::gen_range< / a > 生成 [0, 10) 区间内的随机数( 右开区间，不包括 < code > 10< / code > )。< / p >
< pre > < pre class = "playground" > < code class = "language-rust editable edition2021" > use rand::Rng;
fn main() {
let mut rng = rand::thread_rng();
println!(" Integer: {}" , rng.gen_range(0..10));
println!(" Float: {}" , rng.gen_range(0.0..10.0));
}
< / code > < / pre > < / pre >
< p > < a href = "https://docs.rs/rand/*/rand/distributions/uniform/struct.Uniform.html" > Uniform< / a > 可以用于生成< ruby > 均匀分布< rt > uniform distribution< / rt > < / ruby > 的随机数。当需要在同一个范围内重复生成随机数时，该方法虽然和之前的方法效果一样，但会更快一些。< / p >
< pre > < pre class = "playground" > < code class = "language-rust editable edition2021" > use rand::distributions::{Distribution, Uniform};
fn main() {
let mut 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;
}
}
}
< / code > < / pre > < / pre >
< h3 id = "使用指定分布来生成随机数" > < a class = "header" href = "#使用指定分布来生成随机数" > 使用指定分布来生成随机数< / a > < / h3 >
< p > 默认情况下，< code > rand< / code > 包使用均匀分布来生成随机数，而 < a href = "https://docs.rs/rand_distr/*/rand_distr/index.html" > rand_distr< / a > 包提供了其它类型的分布方式。< / p >
< p > 首先，你需要获取想要使用的分布的实例，然后在 < a href = "https://docs.rs/rand/*/rand/trait.Rng.html" > rand::Rng< / a > 的帮助下使用 < a href = "https://docs.rs/rand/*/rand/distributions/trait.Distribution.html#tymethod.sample" > Distribution::sample< / a > 对该实例进行取样。< / p >
< p > 如果想要查询可用的分布列表，可以访问< a href = "https://docs.rs/rand_distr/*/rand_distr/index.html" > 这里< / a > ，下面的示例中我们将使用 < a href = "https://docs.rs/rand_distr/0.4.3/rand_distr/struct.Normal.html" > Normal< / a > 分布:< / p >
< pre > < pre class = "playground" > < code class = "language-rust editable edition2021" > use rand_distr::{Distribution, Normal, NormalError};
use rand::thread_rng;
fn main() -> Result< (), NormalError> {
let mut 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(())
}
< / code > < / pre > < / pre >
< h3 id = "在自定义类型中生成随机值" > < a class = "header" href = "#在自定义类型中生成随机值" > 在自定义类型中生成随机值< / a > < / h3 >
< p > 使用 < a href = "https://docs.rs/rand/*/rand/distributions/trait.Distribution.html" > Distribution< / a > 特征包裹我们的自定义类型，并为 < a href = "https://docs.rs/rand/*/rand/distributions/struct.Standard.html" > Standard< / a > 实现该特征，可以为自定义类型的指定字段生成随机数。< / p >
< pre > < pre class = "playground" > < code class = "language-rust editable edition2021" > 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() {
let mut rng = rand::thread_rng();
// 生成一个随机的 Point
let rand_point: Point = rng.gen();
println!(" Random Point: {:?}" , rand_point);
// 通过类型暗示( hint )生成一个随机的元组
let rand_tuple = rng.gen::< (i32, bool, f64)> ();
println!(" Random tuple: {:?}" , rand_tuple);
}
< / code > < / pre > < / pre >
< h3 id = "生成随机的字符串a-z-a-z-0-9" > < a class = "header" href = "#生成随机的字符串a-z-a-z-0-9" > 生成随机的字符串(A-Z, a-z, 0-9)< / a > < / h3 >
< p > 通过 < a href = "https://docs.rs/rand/0.8.5/rand/distributions/struct.Alphanumeric.html" > Alphanumeric< / a > 采样来生成随机的 ASCII 字符串，包含从 < code > A-Z, a-z, 0-9< / code > 的字符。< / p >
< pre > < pre class = "playground" > < code class = "language-rust editble edition2021" > 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);
}
< / code > < / pre > < / pre >
< h3 id = "生成随机的字符串-用户指定-ascii-字符-" > < a class = "header" href = "#生成随机的字符串-用户指定-ascii-字符-" > 生成随机的字符串( 用户指定 ASCII 字符 )< / a > < / h3 >
< p > 通过 < a href = "https://docs.rs/rand/0.8.5/rand/trait.Rng.html#method.gen_range" > gen_string< / a > 生成随机的 ASCII 字符串，包含用户指定的字符。< / p >
< pre > < pre class = "playground" > < code class = "language-rust editable edition2021" > fn main() {
use rand::Rng;
const CHARSET: & [u8] = b" ABCDEFGHIJKLMNOPQRSTUVWXYZ\
abcdefghijklmnopqrstuvwxyz\
0123456789)(*& ^%$#@!~" ;
const PASSWORD_LEN: usize = 30;
let mut rng = rand::thread_rng();
let password: String = (0..PASSWORD_LEN)
.map(|_| {
let idx = rng.gen_range(0..CHARSET.len());
CHARSET[idx] as char
})
.collect();
println!(" {:?}" , password);
}
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