A funny thing happened on the way to this column. If you're a regular reader of Programmer's Toolbox and have been following my series on C++ classes for vector and matrix algebra, you may have wondered why you haven't heard from me lately. The reason: I got sick. Real sick. As in, two weeks in hospital sick.

At the time, I had three columns in the works: two Embedded.com online columns and one for the special November issue of Embedded Systems Design. I was working hard to get them out, but was fighting general feelings of weakness, dizzy spells, and shortness of breath. My wife was urging me to see a doctor, but I said, "Not until my columns are finished." I mean, am I devoted, or what?

In the end, though, I couldn't even manage to sit in the chair typing. After one full day in bed, I gave it up and called 911.

I won't bore you with the details, and I promise not to show you my scars. But just to put any grim speculations to rest, we discovered two serious but fixable problems. First, I had developed adult-onset diabetes, which "onsetted" quite suddenly and unexpectedly. Second, I had blood clots in both lungs, each the size of Arizona.

Fortunately, diabetes is easily controlled with diet, exercise, and/or insulin. As for the blood clots, they apparently didn't come from any systemic problem, and the doctors have me on blood thinners and assure me the clots will dissolve in time.

For reasons I can't begin to imagine (except Divine Intervention), I feel surprisingly good. I've lost about 60 lbs. For someone who's not supposed to be able to breath at all, I haven't noticed any shortness of breath. In fact, the more strenuously I exercise, the better I seem to breath. How does that work?

So that's my excuse. The clots ate my homework. Now let's get back to business.

More on reuse
In my last column, I mentioned a problem I was having with Microsoft Visual C++ Express 2005 (VCX). Since it's been awhile, let me recap the situation.

With VCX, you don't build programs, you built "Solutions" and "Projects." By default, VCX installs itself in your My Documents folder, and puts all projects in a folder called ..My Documents\Visual Studio 2005\Projects. Each project gets its own subfolder below that. When I first began developing the vector and matrix classes, I went along with this strategy. I created a project for the vector class and its test driver, and a second project for the matrix class and its test driver.

Later, however, I decided to rearrange things. I tend to keep all my source files in separate folders, one for C, one for C++, etc. Further, I keep the truly reusable source files in a library folder, unimaginatively called jlib. Since the vector class is used in the matrix class, keeping the source files in separate folders makes no sense.