What does “my other car is a cdr” mean?

Question

Can anyone well versed in lisp explain this joke to me? I\'ve done some reading on functional programming languages and know that CAR/CDR mean Contents of Address/Decrement Reg

Answer 1

Yes, definitely a geek joke.

The names come from the IBM 704, but that's not the joke.

The joke is (bad) pun on "my other car is a ___." But the in-joke is about recursion.

When you loop/manipulate/select/invoke/more in lisp you use a combination of car (the first element in the list) and cdr (the rest of the list) to juggle functions.

So you've got a car, but your other car is your cdr because you can always get a car from a cdr since the cdr is always (in recursion) more elements. Get it? Laugh yet?

You'll probably have to learn lisp to actually chuckle a bit, or not. Of course, by then, you'll probably find yourself chuckling randomly for no apparent reason because:

Lisp makes you loopy.