Function combinations 

pub fn combinations(n: u64, k: u64) -> Result<u128, CombinatoricsError>

Returns the number of unordered selections of size k from n items.

Errors

Returns CombinatoricsError::KExceedsN when k > n.

Returns CombinatoricsError::CombinationOverflow when the result no longer fits in u128.

Examples

use use_combinatorics::combinations;

assert_eq!(combinations(5, 2)?, 10);