[brudgers]

That car and cdr can be aliased easily by any Lisp programmer might lead a person to wonder why they survive and are even included in more modern Lisps such as Racket.

The reason is the expressive power of their extended versions - e.g. caadr or cdaar don't have easily derived equivalents from first and rest and those that can be derived are at best equally bad or worse...ffirest and reffst anyone?

[Derbasti]

What's wrong with "second"?

[brudgers]

Nothing and Common Lisp includes second. But that's not caar. It returns the first element of the first element of a list - the extended forms of car and cdr are for nested lists and nested lists can be used to implement many different data structures [and are also the data structure containing Lisp programs].

The extended forms of car and cdr provide a form of expression which is not obvious based on the construction of common non-Lisp languages even those that have very flexible lists and dynamic typing.

[Derbasti]

I know, so do (head (second list)), or if you must, (head2 list) or even (head list 2) or something. Still much more readable than cadr

[AnimalMuppet]

I presume you mean as opposed to "rest".

The problem is, it really is "rest" instead of "second", at least in the usual case. Yes, a cons cell can contain pretty much any two things, but the most-frequently-used case (or so I believe) is that of a list. In that case, "car" means "first element of the list", and "cdr" means "the entire rest of the list", not "the second element of the list".

[frou_dh]

Personally I have found it useful to keep in mind that it's the pair that's fundamental and not the list. IIRC it was pg that made the point somewhere that car and cdr are acceptable because there really aren't any slam-dunk general terms for the parts of a pair.

[AnimalMuppet]

True, and if you're thinking of them as a pair, then "first" and "second" are appropriate. But if you're using them to implement a list, then "second" is misleading.

[frou_dh]

I'd probably go with "left" and "right" to get away from the implication of priority. I didn't type this using my first and second hands.

(bikeshedding acknowledged)