The more annoying thing aboug one-letter variables is about highlighting or finding them (pray you do not have to refactor such code), not so much about understanding what they mean (if the programmer is only somewhat sensible, the purpose of one-letter names is usually still obvious).

But once you find out that your editor lets you conveniently highlight all occurrences of greater-than-N substrings (usually N=3) you start shouting at people who use one-letter variables because it doesn't work with the default settings, nor is there a way you could configure it so it works in a usable way without highlighting every frequently occurring letter in every keyword too.

Well, that's only an argument for getting a better editor. If your editor does not find or highlight single-character variable names out of the box it's already broken.

I was trying to learn about b-trees, and so I looked around and found this implementation, full of one letter variable names:

http://attractivechaos.awardspace.com/kbtree.h.html

then one thinks for a moment "hey, this is where C could use a more powerful preprocessor"...

then thinks for a moment more "I already wrote one before, it didn't help all that much, was inconvinient to use, and generally ended up not really used much...".

but, yes, sadly I have done this sort of thing before, just not usually this much at once, in a few cases (typically for statically-typed interpreter logic and similar, where basically otherwise similar logic has to be repeated endlessly for N-way combinations of types).

I do hope you are being sarcastic

Nope. I do the same with indexes:

i with idx

j with jdx

k with kdx

Indices.

And it's not very object oriented is it?

Consider replacing with

int GetIndex(int idx) { return idx; }

I like the way you code reviewed your edits ;)

I am being sarcastic in case noone noticed.

I was trying to learn about b-trees, and so I looked around and found this implementation, full of one letter variable names:

http://attractivechaos.awardspace.com/kbtree.h.html

THE HORROR.

To the eye of someone who has done years of maintenance programming,and looked at microsofts various SDK samples (and looked at peoples code on this site's forums), that is trivial.

There is the opposite problem of long variable names smearing code statement across multiple lines

Indices.

Indexes, indices, who cares? Both plural forms are valid.