Code Complete, 2nd Edition

Creating Loops Easily—From the Inside Out

If you sometimes have trouble coding a complex loop—which most programmers do— you can use a simple technique to get it right the first time. Here's the general process. Start with one case. Code that case with literals. Then indent it, put a loop around it, and replace the literals with loop indexes or computed expressions. Put another loop around that, if necessary, and replace more literals. Continue the process as long as you have to. When you finish, add all the necessary initializations. Since you start at the simple case and work outward to generalize it, you might think of this as coding from the inside out.

Suppose you're writing a program for an insurance company. It has life-insurance rates that ...