Function two_adic_complexity 

pub fn two_adic_complexity(bits: &[bool]) -> usize

The 2-adic complexity of a bit sequence: ≈ log₂ max(|p|,|q|) for its FCSR rational p/q. Low ⇒ a carry-based keystream (an FCSR / add-with-carry generator); ≈ n/2 for a random sequence.