function test_ismember

x1 = [2;2];
x2 = [2;-2];
x3 = [-2;-2];
x4 = [-2;2];
x = sdpvar(2,1);
P1 = polytope(set(-0.5 < x-x1 < 0.5));
P2 = polytope(set(-0.5 < x-x2 < 0.5));
P3 = polytope(set(-0.5 < x-x3 < 0.5));
P4 = polytope(set(-0.5 < x-x4 < 0.5));
F = ismember(x,[P1 P2 P3 P4]);
sol = solvesdp(F,-sum(x))

mbg_asserttrue(sol.problem == 0)
mbg_asserttolequal(double(x),[2.5;2.5], 1e-4);