cdr

/ku'dr/ or /kuh'dr/ [LISP] To skip past the first item from a

list of things (generalised from the LISP operation on binary

tree structures, which returns a list consisting of all but

the first element of its argument). In the form "cdr down",

to trace down a list of elements: "Shall we cdr down the

agenda?" Usage: silly. See also loop through.

Historical note: The instruction format of the IBM 7090 that

hosted the original LISP implementation featured two 15 bit

fields called the "address" and "decrement" parts. The term

"cdr" was originally "Contents of Decrement part of Register".

Similarly, "car" stood for "Contents of Address part of

Register".

The cdr and car operations have since become bases for

formation of compound metaphors in non-LISP contexts. GLS

recalls, for example, a programming project in which strings

were represented as linked lists; the get-character and

skip-character operations were of course called CHAR and CHDR.

[Jargon File]

(2001-06-22)