  The spatial discretization of the single-cone Dirac Hamiltonian on the
surface of a topological insulator or superconductor needs a special
"staggered" grid, to avoid the appearance of a spurious second cone in the
Brillouin zone. We adapt the Stacey discretization from lattice gauge theory to
produce a generalized eigenvalue problem, of the form ${\mathcal H}\psi=E
{\mathcal P}\psi$, with Hermitian tight-binding operators ${\mathcal H}$,
${\mathcal P}$, a locally conserved particle current, and preserved chiral and
symplectic symmetries. This permits the study of the spectral statistics of
Dirac fermions in each of the four symmetry classes A, AII, AIII, and D.
