Cartesian product of two or more lists: Difference between revisions

=={{header|Common Lisp}}==

<lang lisp>(defun cartesian-product (l)

"Compute the n-cartesian product of a list of sets represented as list with a mixed recursive-iterative approach.

Algorithm:

If there are no sets, then produce an empty set of tuples;

otherwise, for all the elements x of the first set, concatenate the sets obtained by

inserting x at the beginning of each tuple of the n-cartesian product of the remaining sets."

(if (null l)

(list nil)

(loop for x in (car l)

nconc (loop for y in (cartesian-product (cdr l))

collect (cons x y)))))</lang>

Example of use:

<lang lisp>CL-USER> (cartesian-product '((1 2 3) (30) (500 100)))

((1 30 500) (1 30 100) (2 30 500) (2 30 100) (3 30 500) (3 30 100))

</lang>