Re: full/sparse/banded/triangular matrices...

[Paul Kienzle]

LAPACK also has tridiagonal functions.  In the spline code we are
doing a couple of rotations outside the solver so that the cyclic
case doesn't need a full matrix solve.  I doubt you want to support
a mostly banded matrix class though.

Another matrix attribute to consider is a transpose marker, but like
triangular matrices, this only gives a small speedup compared to the
cost of the op.

- Paul