cons

cons /konz/ or /kons/

[from LISP] 1. vt. To add a new element to a specified list, esp. at the top. "OK, cons picking a replacement for the console TTY onto the agenda." 2. `cons up': vt. To synthesize from smaller pieces: "to cons up an example".

In LISP itself, cons is the most fundamental operation for building structures. It takes any two objects and returns a `dot-pair' or two-branched tree with one object hanging from each branch. Because the result of a cons is an object, it can be used to build binary trees of any shape and complexity. Hackers think of it as a sort of universal constructor, and that is where the jargon meanings spring from.

--The Jargon File version 4.3.1, ed. ESR, autonoded by rescdsk.

(foo . bar)

You can put conses within conses, like so:

(foo . (bar . baz))

These make up lists in lisp.