%A = [ 1, 0, -1, 0;
%      0, 1, -1, 0;
%      0, 0,  0, 1 ];
A = [ 1, 0, -1;
      0, 1, -1;
      0, 0,  0 ];

[ Ab, Au ] = PCC_bidirectional_constraints (A);
Ab
Au
