| Note that this is the order of display: The order of display of hunk slots is historical in nature. For better or worse, the elements of a hunk display in order except that the 0th element is last, not first. e.g., for a hunk of a length n+1, (cxr1 . cxr2 . ... . cxrn . cxr0 .) It could still make sense to have the layout in memory being sequential, like (cxr-0 == CDR, cxr-1 == CAR, ...others ...). Note also that CAR extracts the leftmost element of a hunk, just as it addresses the leftmost element of a cons. Similarly, CDR extracts the rightmost element of hunks and conses. It seems more logical that CADR is just the combination of CAR with CDR. It don't think the designers would try to transpose the fact that it means "second", with proper lists, for hunks. It just seems unlikely, but I have no proof. Also: (Note that the operation CAR is undefined on hunk-1's, but CDR is not.) This means that if you want to make a plist for a hunk of your own, you can use its cdr as a hunk; it does not mean that you can blindly assume that any hunk wants its CDR treated that way. The exact use of the slots of a hunk is up to the creator; it's a good idea to mark your hunks (e.g., by placing a distinctive object in their cxr-1 slot) so that you can tell them from hunks created by other programs. My guess is that there is some metadata associated with a hunk, stored in CRX-0, a.k.a. CDR. http://www.maclisp.info/pitmanual/hunks.html |