Association Lists

An association list is a list of dotted pairs in which each left hand side is a symbol:

(setq alist '((a . 1)(b . 2)(c . 3)) )

(setq alist (acons 'x 1 nil))

((X . 1))

(setq alist (acons 'y 2 alist))

((Y . 2)(X . 1))

Association pairs are retrieved using ASSOC:

(assoc 'x alist) ; => (X . 1)

(cdr (assoc 'y alist)) ; => 2