Evaluation of (cons x '()) yields (x), but (cons x nil) yields (x nil) because nil is treated as a boolean value when evaluated instead of as an empty list. The cons of two atoms in newLISP does not yield a dotted pair, but rather a two-element list. The predicate atom? is true for nil, but false for the empty list. The empty list in newLISP is only an empty list and not equal to nil.
A list in newLISP is a LISP cell of type list. It acts like a container for the linked list of elements making up the list cell's contents. There is no dotted pair in newLISP because the cdr (tail) part of a LISP cell always points to another LISP cell and never to a basic data type, such as a number or a symbol. Only the car (head) part may contain a basic data type.
This is why Arc is better than newLISP. The only reason I can think of for this is that newLISP is trying to protect newbies from the actual structure of lists by telling them that cons adds an element to the beginning of a list, car gets the first element of a list, and cdr gets the rest of the list.
Arc doesn't try to protect people from these kinds of things. It's not like we can't handle the real meaning of cons.
