Comment by kazinator
8 years ago
TXR Lisp, a dialect with true conses:
1> (car "abc")
#\a
2> (cdr "abc")
"bc"
3> (cddr "abc")
"c"
4> (cdddr "abc")
nil
5> (caddr "abc")
#\c
8 years ago
TXR Lisp, a dialect with true conses:
1> (car "abc")
#\a
2> (cdr "abc")
"bc"
3> (cddr "abc")
"c"
4> (cdddr "abc")
nil
5> (caddr "abc")
#\c
I'm not sure if that's what you meant, but the point I was addressing was that "first" is bad because you could reasonably expect it to work on anything sequentialish not just on conses (agreed), and car/cdr is explicitly about conses (agreed). But first, in some Lisps, works just fine on everything sequentialish, including vectors and strings, so I don't consider that a particularly strong argument.
cl, cr I could live with, maybe. (consleft, consright). Other suggestions, head and tail, fst and snd, which have some of the other touted advantages. (I don't necessarily agree with them, but they also don't hurt, so...)
car and cdr is not necessarily about conses. I made them the basis for iterating over any list-like sequences in TXR Lisp. To participate in the protocol, an object can implement methods called cdr, car and nullify. This latter nullify should return nil if the object considers itself as representing "empty". Otherwise it can return the object itself, or possibly something else, like an ordinary list.