List

A list is made of two-element data structures, called conses after the function cons that makes them.

• a link , called rest, that points to the next element; or () or nil, an empty list, if there is no next element.

• some contents, called first, as needed for the application. The contents could be a number, a symbol, or a pointer to another linked list.

A list is written inside parentheses:

(list 'a 'b 'c)         ->  (a b c)

(list (+ 2 3) (* 2 3))  ->  (5 6)

We will use the parentheses notation for lists, and nested lists for trees.