Function pack_bits_le

pub fn pack_bits_le<FA, Var, I>(iter: I) -> FA
where
    FA: FieldAlgebra,
    Var: Into<FA> + Clone,
    I: DoubleEndedIterator<Item = Var>,

Pack a collection of bits into a number.

Given vec = [v0, v1, …, v_n] returns v0 + 2v_1 + … + 2^n v_n