pub struct Standard;
Expand description
A generic random value distribution, implemented for many primitive types. Usually generates values with a numerically uniform distribution, and with a range appropriate to the type.
§Provided implementations
Assuming the provided Rng
is well-behaved, these implementations
generate values with the following ranges and distributions:
- Integers (
i32
,u32
,isize
,usize
, etc.): Uniformly distributed over all values of the type. char
: Uniformly distributed over all Unicode scalar values, i.e. all code points in the range0...0x10_FFFF
, except for the range0xD800...0xDFFF
(the surrogate code points). This includes unassigned/reserved code points.bool
: Generatesfalse
ortrue
, each with probability 0.5.- Floating point types (
f32
andf64
): Uniformly distributed in the half-open range[0, 1)
. See notes below. - Wrapping integers (
Wrapping<T>
), besides the type identical to their normal integer variants.
The Standard
distribution also supports generation of the following
compound types where all component types are supported:
- Tuples (up to 12 elements): each element is generated sequentially.
- Arrays (up to 32 elements): each element is generated sequentially;
see also
Rng::fill
which supports arbitrary array length for integer and float types and tends to be faster foru32
and smaller types. When usingrustc
≥ 1.51, enable themin_const_gen
feature to support arrays larger than 32 elements. Note thatRng::fill
andStandard
’s array support are not equivalent: the former is optimised for integer types (using fewer RNG calls for element types smaller than the RNG word size), while the latter supports any element type supported byStandard
. Option<T>
first generates abool
, and if true generates and returnsSome(value)
wherevalue: T
, otherwise returningNone
.
§Custom implementations
The Standard
distribution may be implemented for user types as follows:
use rand::Rng;
use rand::distributions::{Distribution, Standard};
struct MyF32 {
x: f32,
}
impl Distribution<MyF32> for Standard {
fn sample<R: Rng + ?Sized>(&self, rng: &mut R) -> MyF32 {
MyF32 { x: rng.gen() }
}
}
§Example usage
use rand::prelude::*;
use rand::distributions::Standard;
let val: f32 = StdRng::from_entropy().sample(Standard);
println!("f32 from [0, 1): {}", val);
§Floating point implementation
The floating point implementations for Standard
generate a random value in
the half-open interval [0, 1)
, i.e. including 0 but not 1.
All values that can be generated are of the form n * ε/2
. For f32
the 24 most significant random bits of a u32
are used and for f64
the
53 most significant bits of a u64
are used. The conversion uses the
multiplicative method: (rng.gen::<$uty>() >> N) as $ty * (ε/2)
.
See also: Open01
which samples from (0, 1)
, OpenClosed01
which
samples from (0, 1]
and Rng::gen_range(0..1)
which also samples from
[0, 1)
. Note that Open01
uses transmute-based methods which yield 1 bit
less precision but may perform faster on some architectures (on modern Intel
CPUs all methods have approximately equal performance).
Trait Implementations§
Source§impl DistString for Standard
Note: the String
is potentially left with excess capacity; optionally the
user may call string.shrink_to_fit()
afterwards.
impl DistString for Standard
Note: the String
is potentially left with excess capacity; optionally the
user may call string.shrink_to_fit()
afterwards.
Source§impl<T> Distribution<[T; 32]> for Standardwhere
Standard: Distribution<T>,
impl<T> Distribution<[T; 32]> for Standardwhere
Standard: Distribution<T>,
Source§impl<T> Distribution<[T; 31]> for Standardwhere
Standard: Distribution<T>,
impl<T> Distribution<[T; 31]> for Standardwhere
Standard: Distribution<T>,
Source§impl<T> Distribution<[T; 30]> for Standardwhere
Standard: Distribution<T>,
impl<T> Distribution<[T; 30]> for Standardwhere
Standard: Distribution<T>,
Source§impl<T> Distribution<[T; 29]> for Standardwhere
Standard: Distribution<T>,
impl<T> Distribution<[T; 29]> for Standardwhere
Standard: Distribution<T>,
Source§impl<T> Distribution<[T; 28]> for Standardwhere
Standard: Distribution<T>,
impl<T> Distribution<[T; 28]> for Standardwhere
Standard: Distribution<T>,
Source§impl<T> Distribution<[T; 27]> for Standardwhere
Standard: Distribution<T>,
impl<T> Distribution<[T; 27]> for Standardwhere
Standard: Distribution<T>,
Source§impl<T> Distribution<[T; 26]> for Standardwhere
Standard: Distribution<T>,
impl<T> Distribution<[T; 26]> for Standardwhere
Standard: Distribution<T>,
Source§impl<T> Distribution<[T; 25]> for Standardwhere
Standard: Distribution<T>,
impl<T> Distribution<[T; 25]> for Standardwhere
Standard: Distribution<T>,
Source§impl<T> Distribution<[T; 24]> for Standardwhere
Standard: Distribution<T>,
impl<T> Distribution<[T; 24]> for Standardwhere
Standard: Distribution<T>,
Source§impl<T> Distribution<[T; 23]> for Standardwhere
Standard: Distribution<T>,
impl<T> Distribution<[T; 23]> for Standardwhere
Standard: Distribution<T>,
Source§impl<T> Distribution<[T; 22]> for Standardwhere
Standard: Distribution<T>,
impl<T> Distribution<[T; 22]> for Standardwhere
Standard: Distribution<T>,
Source§impl<T> Distribution<[T; 21]> for Standardwhere
Standard: Distribution<T>,
impl<T> Distribution<[T; 21]> for Standardwhere
Standard: Distribution<T>,
Source§impl<T> Distribution<[T; 20]> for Standardwhere
Standard: Distribution<T>,
impl<T> Distribution<[T; 20]> for Standardwhere
Standard: Distribution<T>,
Source§impl<T> Distribution<[T; 19]> for Standardwhere
Standard: Distribution<T>,
impl<T> Distribution<[T; 19]> for Standardwhere
Standard: Distribution<T>,
Source§impl<T> Distribution<[T; 18]> for Standardwhere
Standard: Distribution<T>,
impl<T> Distribution<[T; 18]> for Standardwhere
Standard: Distribution<T>,
Source§impl<T> Distribution<[T; 17]> for Standardwhere
Standard: Distribution<T>,
impl<T> Distribution<[T; 17]> for Standardwhere
Standard: Distribution<T>,
Source§impl<T> Distribution<[T; 16]> for Standardwhere
Standard: Distribution<T>,
impl<T> Distribution<[T; 16]> for Standardwhere
Standard: Distribution<T>,
Source§impl<T> Distribution<[T; 15]> for Standardwhere
Standard: Distribution<T>,
impl<T> Distribution<[T; 15]> for Standardwhere
Standard: Distribution<T>,
Source§impl<T> Distribution<[T; 14]> for Standardwhere
Standard: Distribution<T>,
impl<T> Distribution<[T; 14]> for Standardwhere
Standard: Distribution<T>,
Source§impl<T> Distribution<[T; 13]> for Standardwhere
Standard: Distribution<T>,
impl<T> Distribution<[T; 13]> for Standardwhere
Standard: Distribution<T>,
Source§impl<T> Distribution<[T; 12]> for Standardwhere
Standard: Distribution<T>,
impl<T> Distribution<[T; 12]> for Standardwhere
Standard: Distribution<T>,
Source§impl<T> Distribution<[T; 11]> for Standardwhere
Standard: Distribution<T>,
impl<T> Distribution<[T; 11]> for Standardwhere
Standard: Distribution<T>,
Source§impl<T> Distribution<[T; 10]> for Standardwhere
Standard: Distribution<T>,
impl<T> Distribution<[T; 10]> for Standardwhere
Standard: Distribution<T>,
Source§impl<T> Distribution<[T; 9]> for Standardwhere
Standard: Distribution<T>,
impl<T> Distribution<[T; 9]> for Standardwhere
Standard: Distribution<T>,
Source§impl<T> Distribution<[T; 8]> for Standardwhere
Standard: Distribution<T>,
impl<T> Distribution<[T; 8]> for Standardwhere
Standard: Distribution<T>,
Source§impl<T> Distribution<[T; 7]> for Standardwhere
Standard: Distribution<T>,
impl<T> Distribution<[T; 7]> for Standardwhere
Standard: Distribution<T>,
Source§impl<T> Distribution<[T; 6]> for Standardwhere
Standard: Distribution<T>,
impl<T> Distribution<[T; 6]> for Standardwhere
Standard: Distribution<T>,
Source§impl<T> Distribution<[T; 5]> for Standardwhere
Standard: Distribution<T>,
impl<T> Distribution<[T; 5]> for Standardwhere
Standard: Distribution<T>,
Source§impl<T> Distribution<[T; 4]> for Standardwhere
Standard: Distribution<T>,
impl<T> Distribution<[T; 4]> for Standardwhere
Standard: Distribution<T>,
Source§impl<T> Distribution<[T; 3]> for Standardwhere
Standard: Distribution<T>,
impl<T> Distribution<[T; 3]> for Standardwhere
Standard: Distribution<T>,
Source§impl<T> Distribution<[T; 2]> for Standardwhere
Standard: Distribution<T>,
impl<T> Distribution<[T; 2]> for Standardwhere
Standard: Distribution<T>,
Source§impl<T> Distribution<[T; 1]> for Standardwhere
Standard: Distribution<T>,
impl<T> Distribution<[T; 1]> for Standardwhere
Standard: Distribution<T>,
Source§impl<T> Distribution<[T; 0]> for Standard
impl<T> Distribution<[T; 0]> for Standard
Source§impl Distribution<()> for Standard
impl Distribution<()> for Standard
Source§impl<A> Distribution<(A,)> for Standardwhere
Standard: Distribution<A>,
impl<A> Distribution<(A,)> for Standardwhere
Standard: Distribution<A>,
Source§impl<A, B> Distribution<(A, B)> for Standard
impl<A, B> Distribution<(A, B)> for Standard
Source§impl<A, B, C> Distribution<(A, B, C)> for Standard
impl<A, B, C> Distribution<(A, B, C)> for Standard
Source§impl<A, B, C, D> Distribution<(A, B, C, D)> for Standard
impl<A, B, C, D> Distribution<(A, B, C, D)> for Standard
Source§impl<A, B, C, D, E> Distribution<(A, B, C, D, E)> for Standardwhere
Standard: Distribution<A> + Distribution<B> + Distribution<C> + Distribution<D> + Distribution<E>,
impl<A, B, C, D, E> Distribution<(A, B, C, D, E)> for Standardwhere
Standard: Distribution<A> + Distribution<B> + Distribution<C> + Distribution<D> + Distribution<E>,
Source§impl<A, B, C, D, E, F> Distribution<(A, B, C, D, E, F)> for Standardwhere
Standard: Distribution<A> + Distribution<B> + Distribution<C> + Distribution<D> + Distribution<E> + Distribution<F>,
impl<A, B, C, D, E, F> Distribution<(A, B, C, D, E, F)> for Standardwhere
Standard: Distribution<A> + Distribution<B> + Distribution<C> + Distribution<D> + Distribution<E> + Distribution<F>,
Source§impl<A, B, C, D, E, F, G> Distribution<(A, B, C, D, E, F, G)> for Standardwhere
Standard: Distribution<A> + Distribution<B> + Distribution<C> + Distribution<D> + Distribution<E> + Distribution<F> + Distribution<G>,
impl<A, B, C, D, E, F, G> Distribution<(A, B, C, D, E, F, G)> for Standardwhere
Standard: Distribution<A> + Distribution<B> + Distribution<C> + Distribution<D> + Distribution<E> + Distribution<F> + Distribution<G>,
Source§impl<A, B, C, D, E, F, G, H> Distribution<(A, B, C, D, E, F, G, H)> for Standardwhere
Standard: Distribution<A> + Distribution<B> + Distribution<C> + Distribution<D> + Distribution<E> + Distribution<F> + Distribution<G> + Distribution<H>,
impl<A, B, C, D, E, F, G, H> Distribution<(A, B, C, D, E, F, G, H)> for Standardwhere
Standard: Distribution<A> + Distribution<B> + Distribution<C> + Distribution<D> + Distribution<E> + Distribution<F> + Distribution<G> + Distribution<H>,
Source§fn sample<R>(&self, _rng: &mut R) -> (A, B, C, D, E, F, G, H)
fn sample<R>(&self, _rng: &mut R) -> (A, B, C, D, E, F, G, H)
T
, using rng
as the source of randomness.Source§impl<A, B, C, D, E, F, G, H, I> Distribution<(A, B, C, D, E, F, G, H, I)> for Standardwhere
Standard: Distribution<A> + Distribution<B> + Distribution<C> + Distribution<D> + Distribution<E> + Distribution<F> + Distribution<G> + Distribution<H> + Distribution<I>,
impl<A, B, C, D, E, F, G, H, I> Distribution<(A, B, C, D, E, F, G, H, I)> for Standardwhere
Standard: Distribution<A> + Distribution<B> + Distribution<C> + Distribution<D> + Distribution<E> + Distribution<F> + Distribution<G> + Distribution<H> + Distribution<I>,
Source§fn sample<R>(&self, _rng: &mut R) -> (A, B, C, D, E, F, G, H, I)
fn sample<R>(&self, _rng: &mut R) -> (A, B, C, D, E, F, G, H, I)
T
, using rng
as the source of randomness.Source§impl<A, B, C, D, E, F, G, H, I, J> Distribution<(A, B, C, D, E, F, G, H, I, J)> for Standardwhere
Standard: Distribution<A> + Distribution<B> + Distribution<C> + Distribution<D> + Distribution<E> + Distribution<F> + Distribution<G> + Distribution<H> + Distribution<I> + Distribution<J>,
impl<A, B, C, D, E, F, G, H, I, J> Distribution<(A, B, C, D, E, F, G, H, I, J)> for Standardwhere
Standard: Distribution<A> + Distribution<B> + Distribution<C> + Distribution<D> + Distribution<E> + Distribution<F> + Distribution<G> + Distribution<H> + Distribution<I> + Distribution<J>,
Source§fn sample<R>(&self, _rng: &mut R) -> (A, B, C, D, E, F, G, H, I, J)
fn sample<R>(&self, _rng: &mut R) -> (A, B, C, D, E, F, G, H, I, J)
T
, using rng
as the source of randomness.Source§impl<A, B, C, D, E, F, G, H, I, J, K> Distribution<(A, B, C, D, E, F, G, H, I, J, K)> for Standardwhere
Standard: Distribution<A> + Distribution<B> + Distribution<C> + Distribution<D> + Distribution<E> + Distribution<F> + Distribution<G> + Distribution<H> + Distribution<I> + Distribution<J> + Distribution<K>,
impl<A, B, C, D, E, F, G, H, I, J, K> Distribution<(A, B, C, D, E, F, G, H, I, J, K)> for Standardwhere
Standard: Distribution<A> + Distribution<B> + Distribution<C> + Distribution<D> + Distribution<E> + Distribution<F> + Distribution<G> + Distribution<H> + Distribution<I> + Distribution<J> + Distribution<K>,
Source§fn sample<R>(&self, _rng: &mut R) -> (A, B, C, D, E, F, G, H, I, J, K)
fn sample<R>(&self, _rng: &mut R) -> (A, B, C, D, E, F, G, H, I, J, K)
T
, using rng
as the source of randomness.Source§impl<A, B, C, D, E, F, G, H, I, J, K, L> Distribution<(A, B, C, D, E, F, G, H, I, J, K, L)> for Standardwhere
Standard: Distribution<A> + Distribution<B> + Distribution<C> + Distribution<D> + Distribution<E> + Distribution<F> + Distribution<G> + Distribution<H> + Distribution<I> + Distribution<J> + Distribution<K> + Distribution<L>,
impl<A, B, C, D, E, F, G, H, I, J, K, L> Distribution<(A, B, C, D, E, F, G, H, I, J, K, L)> for Standardwhere
Standard: Distribution<A> + Distribution<B> + Distribution<C> + Distribution<D> + Distribution<E> + Distribution<F> + Distribution<G> + Distribution<H> + Distribution<I> + Distribution<J> + Distribution<K> + Distribution<L>,
Source§fn sample<R>(&self, _rng: &mut R) -> (A, B, C, D, E, F, G, H, I, J, K, L)
fn sample<R>(&self, _rng: &mut R) -> (A, B, C, D, E, F, G, H, I, J, K, L)
T
, using rng
as the source of randomness.