At the end of Supplement 4, I asked you to write a version of
would drive a coal trader, but not to worry about fuel. Can you add a
clause that will buy fuel if he has fewer than 10 units remaining?
You will find one possible answer in COLLIER2. The comparison operators allow you to program a test on the amount of fuel, but not to calculate the amount to buy as a function of other quantities. So thus far, you will have to write the amount in as a constant number. The next lesson deals with arithmetic, and shows you how to do such calculations.