Examples used to test the program:
------ simplex
0,max,2,4
5,4
6,4,<=,24
1,2,<=,6
-1,1,<=,1
0,1,<=,2
0,max,4,3
3,-1,3,4
1,2,2,4,<=,40
2,-1,1,2,<=,8
4,-2,1,-1,<=,10
0,max,3,3
1,-7,3
2,1,-1,<=,4
4,-3,0,<=,2
-3,2,1,<=,3
------ Degenerate solution
0,max,2,2
3,9
1,4,<=,8
1,2,<=,4
------ U is not bounded
0,max,3,3
20,10,1
3,-3,5,<=,50
1,0,1,<=,10
1,-1,4,<=,20
------ Two phases
2,min,2,3
0.4,0.5
0.3,0.1,<=,2.7
0.5,0.5,=,6
0.6,0.4,>=,6
2,max,2,3
3,5
1,0,<=,4
0,2,<=,12
3,2,=,18
2,min,3,3
2,3,-4
5,6,7,<=,8
9,10,11,=,12
3,14,15,>=,16
------ Big M
1,max,2,3
3,5
1,0,<=,4
0,2,<=,12
3,2,=,18
1,min,2,3
0.4,0.5
0.3,0.1,<=,2.7
0.5,0.5,=,6
0.6,0.4,>=,6
2,min,3,3
2,3,-4
5,6,7,<=,8
9,10,11,=,12
3,14,15,>=,16
------ Solution is not feasible
1,max,2,2
5,4
2,1,<=,2
3,4,>=,12
------ Multiple solutions
2,max,2,3
2000,3000
1,1,>=,4
2,3,<=,10
400,200,>=,1200