Return the next random u32.

This rarely needs to be called directly, prefer r.gen() to r.next_u32().

Return the next random u64.

By default this is implemented in terms of next_u32. An implementation of this trait must provide at least one of these two methods. Similarly to next_u32, this rarely needs to be called directly, prefer r.gen() to r.next_u64().

Fill dest with random data.

This has a default implementation in terms of next_u64 and next_u32, but should be overridden by implementations that offer a more efficient solution than just calling those methods repeatedly.

This method does not have a requirement to bear any fixed relationship to the other methods, for example, it does not have to result in the same output as progressively filling dest with self.gen::<u8>(), and any such behaviour should not be relied upon.

This method should guarantee that dest is entirely filled with new data, and may fail if this is impossible (e.g. reading past the end of a file that is being used as the source of randomness).

Example

use std::rand::{task_rng, Rng};

let mut v = [0u8, .. 13579];
task_rng().fill_bytes(v);
println!("{}", v.as_slice());

Return a random value of a Rand type.

Example

use std::rand::{task_rng, Rng};

let mut rng = task_rng();
let x: uint = rng.gen();
println!("{}", x);
println!("{}", rng.gen::<(f64, bool)>());

Return an iterator which will yield an infinite number of randomly generated items.

Example

use std::rand::{task_rng, Rng};

let mut rng = task_rng();
let x = rng.gen_iter::<uint>().take(10).collect::<Vec<uint>>();
println!("{}", x);
println!("{}", rng.gen_iter::<(f64, bool)>().take(5)
                  .collect::<Vec<(f64, bool)>>());

Generate a random value in the range [low, high). Fails if low >= high.

This is a convenience wrapper around distributions::Range. If this function will be called repeatedly with the same arguments, one should use Range, as that will amortize the computations that allow for perfect uniformity, as they only happen on initialization.

Example

use std::rand::{task_rng, Rng};

let mut rng = task_rng();
let n: uint = rng.gen_range(0u, 10);
println!("{}", n);
let m: f64 = rng.gen_range(-40.0f64, 1.3e5f64);
println!("{}", m);

Return a bool with a 1 in n chance of true

Example

use std::rand::{task_rng, Rng};

let mut rng = task_rng();
println!("{:b}", rng.gen_weighted_bool(3));

Return an iterator of random characters from the set A-Z,a-z,0-9.

Example

use std::rand::{task_rng, Rng};

let s: String = task_rng().gen_ascii_chars().take(10).collect();
println!("{}", s);

Return a random element from values.

Return None if values is empty.

Example

use std::rand::{task_rng, Rng};

let choices = [1i, 2, 4, 8, 16, 32];
let mut rng = task_rng();
println!("{}", rng.choose(choices));
assert_eq!(rng.choose(choices.slice_to(0)), None);

Deprecated name for choose().

Shuffle a mutable slice in place.

Example

use std::rand::{task_rng, Rng};

let mut rng = task_rng();
let mut y = [1i, 2, 3];
rng.shuffle(y);
println!("{}", y.as_slice());
rng.shuffle(y);
println!("{}", y.as_slice());