I find code easier to read when the names are easily spoken aloud. In the language I'm working on (nothing serious) all the common names are either English words or things that look like English words. I also favor short words over long words and Germanic words over Latin words, and I avoid abbreviations as much as possible (except in local variables, which are usually single letters). It helps me a lot.
As to car/cdr specifically, though, I think the best option is pattern matching.
Well, cdr can't really be spoken aloud unless you make up a way to pronounce it (which of course people do). And you could do the same for hp, rp, and the rest... adding an "o" sound gives some nice words, like hop, top, and fop. Kind of a Dr. Suess feel. :)
Yes, but IMHO they are omogeneous with the other abbrevs in Arc sintax and are also conceptually clearer than car/cdr (that refer to old registers of an old pc): for example, hp (head of pair), tp (tail of pair) and hthtp (head tail head tail of pair) may help conceptual visualization...
