I am with Erik: ALWAYS have code there to handle traps for things that will "never" happen. I usually start with a vector to a loop as described. One tip I have learned: Put the same comment (something like ***TBA***) on each of the vector lines. That lets me go back when I am doing code clean-up and find all of my unfinished code. Like Erik said, I usually don't know how to handle the exceptions until the code is mostly complete.