Function malachite_base::sets::exhaustive::exhaustive_b_tree_sets_length_range

source · 
pub fn exhaustive_b_tree_sets_length_range<I: Clone + Iterator>(
    a: u64,
    b: u64,
    xs: I
) -> ExhaustiveOrderedUniqueCollections<I, BTreeSet<I::Item>> ⓘ
where
    I::Item: Clone + Ord,
Expand description

Generates BTreeSets, with lengths in a range $[a, b)$, with elements from a single iterator.

The source iterator should not repeat any elements, but this is not enforced.

The iterator should be finite; if it is infinite, only prefixes of the iterator will be generated.

If $a \leq b$, the output is empty.

If $a = 0$ and $b = 1$, the output consists of a single empty BTreeSet.

If the input iterator is infinite and $0 < a < b$, the output length is also infinite.

If the input iterator length is $n$, the output length is $$ \sum_{i=a}^b - 1 \binom{n}{i}. $$

§Examples

#[macro_use]
extern crate maplit;

use itertools::Itertools;
use malachite_base::sets::exhaustive::exhaustive_b_tree_sets_length_range;

fn main() {
    let xss = exhaustive_b_tree_sets_length_range(2, 4, 1..=4).collect_vec();
    assert_eq!(
        xss,
        &[
            btreeset!{1, 2},
            btreeset!{1, 3},
            btreeset!{2, 3},
            btreeset!{1, 2, 3},
            btreeset!{1, 4},
            btreeset!{2, 4},
            btreeset!{1, 2, 4},
            btreeset!{3, 4},
            btreeset!{1, 3, 4},
            btreeset!{2, 3, 4}
        ]
    );
}