This is very cool! How does it compare with the features offered by GLPK? It seems to solve a super-set of glpk's problems? What are the tradeoffs of this generalization?
grid =
Int8[0 0 0 5 4 6 0 0 9
0 2 0 0 0 0 0 0 7
0 0 3 9 0 0 0 0 4
9 0 5 0 0 0 0 7 0
7 0 0 0 0 0 0 2 0
0 0 0 0 9 3 0 0 0
0 5 6 0 0 8 0 0 0
0 1 0 0 3 9 0 0 0
0 0 0 0 0 0 8 0 6] Int8[0 0 0 5 4 6 0 0 9;
0 2 0 0 0 0 0 0 7;
0 0 3 9 0 0 0 0 4;
9 0 5 0 0 0 0 7 0;
7 0 0 0 0 0 0 2 0;
0 0 0 0 9 3 0 0 0;
0 5 6 0 0 8 0 0 0;
0 1 0 0 3 9 0 0 0;
0 0 0 0 0 0 8 0 6]