option instead of an int. If we divide 6 by 2, we get the answer Just
3. But if we divide 6 by 0, we get the answer Nothing.
-The next step was to adjust the other arithmetic functions to know how
-to handle receiving Nothing instead of a (boxed) integer. This meant
+The next step was to adjust the other arithmetic functions to teach them what to do if they received Nothing instead of a boxed integer.
+This meant
changing the type of their input from ints to int options. But we
didn't need to do this piecemeal; rather, we could "lift" the ordinary
arithmetic operations into the monad using the various tools provided