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Use gen_range instead of rand::choose (#527)

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lzutao 2019-04-16 11:13:45 +07:00 • committed by Andrew Gauger
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25
src/algorithms/randomness/rand-choose.md
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@ -2,25 +2,30 @@
[![rand-badge]][rand] [![cat-os-badge]][cat-os] [![rand-badge]][rand] [![cat-os-badge]][cat-os]
Randomly generates a string of given length ASCII characters with custom user-defined bytestring, with [`choose`]. Randomly generates a string of given length ASCII characters with custom
user-defined bytestring, with [`gen_range`].
```rust ```rust
extern crate rand; extern crate rand;
use rand::seq::SliceRandom;
fn main() { fn main() {
const CHARSET: &[u8] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZ\ use rand::Rng;
abcdefghijklmnopqrstuvwxyz\ const CHARSET: &[u8] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZ\
0123456789)(*&^%$#@!~"; abcdefghijklmnopqrstuvwxyz\
0123456789)(*&^%$#@!~";
const PASSWORD_LEN: usize = 30;
let mut rng = rand::thread_rng(); let mut rng = rand::thread_rng();
let password: Option<String> = (0..30)
.map(|_| Some(*CHARSET.choose(&mut rng)? as char)) let password: String = (0..PASSWORD_LEN)
.map(|_| {
let idx = rng.gen_range(0, CHARSET.len());
// This is safe because `idx` is in range of `CHARSET`
char::from(unsafe { *CHARSET.get_unchecked(idx) })
})
.collect(); .collect();
println!("{:?}", password); println!("{:?}", password);
} }
``` ```
[`choose`]: https://docs.rs/rand/*/rand/trait.Rng.html#method.choose [`gen_range`]: https://docs.rs/rand/*/rand/trait.Rng.html#method.gen_range