Past exam of the computer science course of the University of Oxford / 2015 / Object oriented programming / 3 / c

For an integer cell coordinate, occupancy is an existential predicate:The first occupied unit cell of brick $i$ is at $x_i$, and its last is at $x_i+w_i-1$. Thus the required support predicate, with the baseplate explicitly included, isFor width one, the two support cells coincide. For a wider brick, its middle may bridge an empty gap; the question only requires support beneath its two ends. Checking $x_i+w_i$ would incorrectly examine a cell beyond the brick's right end. The potentially infinite baseplate supplies every required support at height zero.^[ref]