ToC DocOverview CGDoc RelNotes Index PermutedIndex
Allegro CL

ANSI Common Lisp   14 Conses   14.2 Dictionary of Conses

 14.2.10 copy-tree Function

Syntax:
copy-tree tree    new-tree

Arguments and Values:
tree - a tree.

new-tree - a tree.

Description:
Creates 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.

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))
```