Number of ℚ-components

The number of $\mathbb Q$-irreducible components of the characteristic-zero realization space; 0 when the matroid is not realizable in characteristic 0. A $\mathbb Q$-component may split into several conjugate components over $\overline{\mathbb Q}$, so this is at most rs_n_qbar_components.

For rank 2, rank 3 on at most 11 elements and rank 4 on at most 9, read off from birational_type_components.