wolffd@0: function v = wrap(u,N)
wolffd@0: % WRAP Wrap a vector of indices around a torus.
wolffd@0: % v = wrap(u,N)
wolffd@0: %
wolffd@0: % e.g., wrap([-1 0 1 2 3 4], 3)   =   2 3 1 2 3 1
wolffd@0: 
wolffd@0: v = mod(u-1,N)+1;