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1# fastrand
2
3[![Build](https://github.com/smol-rs/fastrand/workflows/Build%20and%20test/badge.svg)](
4https://github.com/smol-rs/fastrand/actions)
5[![License](https://img.shields.io/badge/license-Apache--2.0_OR_MIT-blue.svg)](
6https://github.com/smol-rs/fastrand)
7[![Cargo](https://img.shields.io/crates/v/fastrand.svg)](
8https://crates.io/crates/fastrand)
9[![Documentation](https://docs.rs/fastrand/badge.svg)](
10https://docs.rs/fastrand)
11
12A simple and fast random number generator.
13
14The implementation uses [Wyrand](https://github.com/wangyi-fudan/wyhash), a simple and fast
15generator but **not** cryptographically secure.
16
17## Examples
18
19Flip a coin:
20
21```rust
22if fastrand::bool() {
23    println!("heads");
24} else {
25    println!("tails");
26}
27```
28
29Generate a random `i32`:
30
31```rust
32let num = fastrand::i32(..);
33```
34
35Choose a random element in an array:
36
37```rust
38let v = vec![1, 2, 3, 4, 5];
39let i = fastrand::usize(..v.len());
40let elem = v[i];
41```
42
43Shuffle an array:
44
45```rust
46let mut v = vec![1, 2, 3, 4, 5];
47fastrand::shuffle(&mut v);
48```
49
50Generate a random `Vec` or `String`:
51
52```rust
53use std::iter::repeat_with;
54
55let v: Vec<i32> = repeat_with(|| fastrand::i32(..)).take(10).collect();
56let s: String = repeat_with(fastrand::alphanumeric).take(10).collect();
57```
58
59To get reproducible results on every run, initialize the generator with a seed:
60
61```rust
62// Pick an arbitrary number as seed.
63fastrand::seed(7);
64
65// Now this prints the same number on every run:
66println!("{}", fastrand::u32(..));
67```
68
69To be more efficient, create a new `Rng` instance instead of using the thread-local
70generator:
71
72```rust
73use std::iter::repeat_with;
74
75let rng = fastrand::Rng::new();
76let mut bytes: Vec<u8> = repeat_with(|| rng.u8(..)).take(10_000).collect();
77```
78
79## License
80
81Licensed under either of
82
83 * Apache License, Version 2.0 ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)
84 * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
85
86at your option.
87
88#### Contribution
89
90Unless you explicitly state otherwise, any contribution intentionally submitted
91for inclusion in the work by you, as defined in the Apache-2.0 license, shall be
92dual licensed as above, without any additional terms or conditions.
93