Suppose I tell you that I have written a Fortran function that solves equations of the form
where P and Q are real-valued constants and e is the base of the natural logarithm (approximately 2.718281828).
Suppose further that, as luck would have it, you could make use of just such a function in a program that you are currently writing. What exactly do you need to know about my function in order to use it in your program? (Obviously, you'll eventually need to get your hands on the code in order to combine it with your code, but let's not worry about that just now.) Think carefully about the question before you look at the answer.
You now have enough information to be able to write a program that uses my function.
Hamlet Project