Function malachite_base::sets::random::random_hash_sets

source · [−]

pub fn random_hash_sets<I: Iterator>(
    seed: Seed, 
    xs_gen: &dyn Fn(Seed) -> I, 
    mean_length_numerator: u64, 
    mean_length_denominator: u64
) -> RandomHashSets<I::Item, GeometricRandomNaturalValues<u64>, I>ⓘNotable traits for RandomHashSets<T, I, J>impl<T: Eq + Hash, I: Iterator<Item = u64>, J: Iterator<Item = T>> Iterator for RandomHashSets<T, I, J>    type Item = HashSet<T>; where
    I::Item: Eq + Hash,

Expand description

Generates random HashSets using elements from an iterator.

The lengths of the HashSets are sampled from a geometric distribution with a specified mean $m$, equal to mean_length_numerator / mean_length_denominator. $m$ must be greater than 0.

Strictly speaking, the input iterator must generate infinitely many distinct elements. In practice it only needs to generate $k$ distinct elements, where $k$ is the largest length actually sampled from the geometric distribution. For example, if mean_length_numerator / mean_length_denominator is significantly lower than 256, then it’s ok to use random_unsigneds::<u8>.

$$ P((x_i)_{i=0}^{n-1}) = n!P_g(n)\prod_{i=0}^{n-1}P(x_i), $$ where $P_g(n)$ is the probability function described in geometric_random_unsigneds.

xs_gen must be infinite.

Panics

Panics if mean_length_numerator or mean_length_denominator are zero, or, if after being reduced to lowest terms, their sum is greater than or equal to $2^{64}$.

Examples

extern crate itertools;
#[macro_use]
extern crate maplit;

use itertools::Itertools;
use malachite_base::num::random::random_primitive_ints;
use malachite_base::random::EXAMPLE_SEED;
use malachite_base::sets::random::random_hash_sets;

fn main() {
    let xs = random_hash_sets(EXAMPLE_SEED, &random_primitive_ints::<u8>, 4, 1);
    let values = xs.take(20).collect_vec();
    assert_eq!(
        values,
        &[
            hashset!{},
            hashset!{11, 32, 38, 85, 134, 136, 162, 166, 177, 200, 203, 217, 223, 235},
            hashset!{30, 90, 218, 234},
            hashset!{9, 106, 204, 216},
            hashset!{151},
            hashset!{},
            hashset!{78, 91, 97, 213, 253},
            hashset!{39, 191},
            hashset!{170, 175, 232, 233},
            hashset!{},
            hashset!{2, 22, 35, 114, 198, 217},
            hashset!{},
            hashset!{},
            hashset!{17, 25, 32, 65, 79, 114, 121, 144, 148, 173, 222},
            hashset!{52, 69, 73, 91, 115, 137, 153, 178},
            hashset!{},
            hashset!{34, 95, 112},
            hashset!{},
            hashset!{106, 130, 167, 168, 197},
            hashset!{86, 101, 122, 150, 172, 177, 207, 218, 221}
        ]
    );
}