Function copy-tree

Syntax:

Arguments and Values:

tree—a tree.

new-tree—a tree.

Description:

15.2.0 25Creates a copy of a tree of conses.

If tree is not a cons, it is returned; otherwise, the result is a new cons of the results of calling copy-tree on the car and cdr of tree. In other words, all conses in the tree represented by tree are copied recursively, stopping only when non-conses are encountered.

copy-tree does not preserve circularities and the sharing of substructure. !!! And consequently might fail to return in the case of circularity? -kmp 09-Apr-91

Examples:

 (setq object (list (cons 1 "one")
                    (cons 2 (list 'a 'b 'c))))
→ ((1 . "one") (2 A B C))
 (setq object-too object) → ((1 . "one") (2 A B C))
 (setq copy-as-list (copy-list object))
 (setq copy-as-alist (copy-alist object))
 (setq copy-as-tree (copy-tree object))
 (eq object object-too) → true
 (eq copy-as-tree object) → false
 (eql copy-as-tree object) → false
 (equal copy-as-tree object) → true
 (setf (first (cdr (second object))) "a"
       (car (second object)) "two"
       (car object) '(one . 1)) → (ONE . 1)
 object → ((ONE . 1) ("two" "a" B C))
 object-too → ((ONE . 1) ("two" "a" B C))
 copy-as-list → ((1 . "one") ("two" "a" B C))
 copy-as-alist → ((1 . "one") (2 "a" B C))
 copy-as-tree → ((1 . "one") (2 A B C)) 

Side Effects:

None.

Affected By:

None.

Exceptional Situations:

None.

See Also:

tree-equal

Notes:

None.