Function rand::random

source · [−]

pub fn random<T>() -> Twhere
    Standard: Distribution<T>,

Expand description

Generates a random value using the thread-local random number generator.

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This is simply a shortcut for thread_rng().gen(). See thread_rng for -documentation of the entropy source and Standard for documentation of -distributions and type-specific generation.

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Provided implementations

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The following types have provided implementations that -generate values with the following ranges and distributions:

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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 range 0...0x10_FFFF, except for the range -0xD800...0xDFFF (the surrogate code points). This includes -unassigned/reserved code points.
bool: Generates false or true, each with probability 0.5.
Floating point types (f32 and f64): 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.

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Also supported is the generation of the following -compound types where all component types are supported:

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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 -types and tends to be faster for u32 and smaller types.
Option<T> first generates a bool, and if true generates and returns -Some(value) where value: T, otherwise returning None.

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Examples

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let x = rand::random::<u8>();
-println!("{}", x);
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-let y = rand::random::<f64>();
-println!("{}", y);
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-if rand::random() { // generates a boolean
-    println!("Better lucky than good!");
-}

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If you’re calling random() in a loop, caching the generator as in the -following example can increase performance.

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use rand::Rng;
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-let mut v = vec![1, 2, 3];
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-for x in v.iter_mut() {
-    *x = rand::random()
-}
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-// can be made faster by caching thread_rng
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-let mut rng = rand::thread_rng();
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-for x in v.iter_mut() {
-    *x = rng.gen();
-}

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