Function combine_limbs_m_to_n 

pub fn combine_limbs_m_to_n<const M: usize, const N: usize, const BITSIZE_M: usize, const BITSIZE_N: usize, F: PrimeField, V: Add<V, Output = V> + Sub<V, Output = V> + Mul<V, Output = V> + Neg<Output = V> + From<u64> + Clone, Func: Fn(F) -> V>(
    from_field: Func,
    x: [V; M],
) -> [V; N]

Helper function for limb recombination.

Combines an array of M elements (think N_LIMBS_SMALL) into an array of N elements (think N_LIMBS_LARGE) elements by taking chunks a_i of size K = BITSIZE_N / BITSIZE_M from the first, and recombining them as a_i * 2^{i * 2^LIMB_BITSIZE_SMALL}.