cons (FUNTION)

Format: (cons <exp1> <exp2>)

Required arguments: 2

<exp1>: any LISP expression <exp2>: any LISP expression

Both argument expressions are evaluated. In common usage, the second expression usually returns a list. In this case, cons creates a new copy of the list returned by <expr2>, and makes the value returned by <expr1> the new first element in this list. However, if <expr2> returns an atom, cons returns the dotted pair of the values of the two expressions.

Examples:

> (cons 'a '(1 2 3))
(A 1 2 3)

> (cons '(a) '(1 2 3))
((A) 1 2 3)

> (setq a 3)
3
> (cons a (list i j k))
(3 I J K)

> (cons 'a a)
(A . 3)                           ;;a dotted pair

> (cons '(1 2) 'q)
((1 2) . Q)                       ;;another dotted pair