>>> x (0), ze (1), y (2), zs (3)
>>> 3
>>> (y&x)
>>> (!y)
>>> (!ze)
>>> Invalid mode: 3
>>> False
>>> True
>>> True
>>> 0 0
0 1
1 0
1 1
---
>>> 0 0
1 0
---
>>> x
---
>>> >>> True
>>> >>> False
>>> >>> >>> True
>>> 1
>>> 1
>>> Inf
>>> 