Function affine_subspace_agl_order 

pub fn affine_subspace_agl_order(n: u32, k: u32) -> u128

The affine automorphism group order of a k-dimensional affine subspace of GF(2)ⁿ — i.e. the number of affine maps x ↦ Ax ⊕ b fixing the model set of an XOR-defined family whose solution space has dimension k. In closed form, computable at every n without enumerating AGL(n,2): |GL(k,2)| · |GL(n−k,2)| · 2^{k(n−k)} · 2^k — the block-upper-triangular invertible linear parts (GL(k) on the subspace, GL(n−k) on the quotient, 2^{k(n−k)} shears between them) times the 2^k in-subspace translations. The scalable affine-symmetry detector for the whole class of linear families: Bₙ sees a vanishing fraction of it (see the tests).