Function factorial 

pub const fn factorial(n: u64) -> Result<u128, CombinatoricsError>

Returns n! using checked u128 arithmetic.

Overflow begins at n = 35.

Errors

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

Examples

use use_combinatorics::factorial;

assert_eq!(factorial(5)?, 120);