Suppose you have an indexed list of variables say :
x = var("x", n=11)
Z=list(x)
and a list of conditions :
Cond = [x_1 >=0, x_2==0, x_6<=0]
First I am not sure that x_1 refers to the indexed variable with the same index. Then how to make a list of variables for which there is no condition inside Cond.
