--- avl-tree1.el 2009-11-22 22:15:16.000000000 +0000 +++ avl-tree2.el 2009-11-22 22:15:20.000000000 +0000 @@ -6,7 +6,7 @@ ;; Inge Wallin ;; Thomas Bellman ;; modified by Toby Cubitt -;; Version: 0.1 +;; Version: 0.2 ;; Maintainer: FSF ;; Created: 10 May 1991 ;; Keywords: extensions, data structures, AVL, tree @@ -54,6 +54,13 @@ ;;; Change log: ;; +;; Version 0.2 +;; * added new optional arguments to `avl-tree-member', `avl-tree-enter' +;; and `avl-tree-delete' +;; * added `avl-tree-member-p', `avl-tree-mapc', `avl-tree-mapcar', +;; `avl-tree-mapf', `avl-tree-stack', `avl-tree-stack-pop' and +;; `avl-tree-stack-first' functions +;; ;; Version 0.1 ;; * simplified rebalancing code ;; * added optional direction argument to `avl-tree-map' @@ -211,36 +218,49 @@ (avl-tree--node-left br)) t))) -(defun avl-tree--do-delete (cmpfun root branch data) - ;; Return t if the height of the tree has shrunk. +(defun avl-tree--do-delete (cmpfun root branch data test nilflag) + ;; Return ( . ), where is t if the height of + ;; the tree has shrunk and nil otherwise, and is the releted + ;; data. (let ((br (avl-tree--node-branch root branch))) (cond + ;; DATA not in tree. ((null br) - nil) + (cons nil nilflag)) ((funcall cmpfun data (avl-tree--node-data br)) - (if (avl-tree--do-delete cmpfun br 0 data) - (avl-tree--del-balance root branch 0))) + (let ((ret (avl-tree--do-delete cmpfun br 0 data test nilflag))) + (cons (if (car ret) (avl-tree--del-balance root branch 0)) + (cdr ret)))) ((funcall cmpfun (avl-tree--node-data br) data) - (if (avl-tree--do-delete cmpfun br 1 data) - (avl-tree--del-balance root branch 1))) + (let ((ret (avl-tree--do-delete cmpfun br 1 data test nilflag))) + (cons (if (car ret) (avl-tree--del-balance root branch 1)) + (cdr ret)))) + + (t ; Found it. + ;; if it fails TEST, do nothing + (if (and test (not (funcall test (avl-tree--node-data br)))) + (cons nil nilflag) + (cond + ((null (avl-tree--node-right br)) + (setf (avl-tree--node-branch root branch) + (avl-tree--node-left br)) + (cons t (avl-tree--node-data br))) + + ((null (avl-tree--node-left br)) + (setf (avl-tree--node-branch root branch) + (avl-tree--node-right br)) + (cons t (avl-tree--node-data br))) + + (t + (if (avl-tree--do-del-internal br 0 br) + (cons (avl-tree--del-balance root branch 0) + (avl-tree--node-data br)) + (cons nil (avl-tree--node-data br)))) + )))))) + - (t - ;; Found it. Let's delete it. - (cond - ((null (avl-tree--node-right br)) - (setf (avl-tree--node-branch root branch) (avl-tree--node-left br)) - t) - - ((null (avl-tree--node-left br)) - (setf (avl-tree--node-branch root branch) - (avl-tree--node-right br)) - t) - - (t - (if (avl-tree--do-del-internal br 0 br) - (avl-tree--del-balance root branch 0)))))))) ;; ---------------------------------------------------------------- ;; Entering data @@ -295,27 +315,42 @@ (avl-tree--node-branch node branch)) 0)) nil)))) -(defun avl-tree--do-enter (cmpfun root branch data) - ;; Return t if height of tree ROOT has grown. INTERNAL USE ONLY. +(defun avl-tree--do-enter (cmpfun root branch data &optional updatefun) + ;; Return cons cell ( . ), where is t if height of + ;; tree ROOT has grown and nil otherwise, and is the inserted + ;; data. (let ((br (avl-tree--node-branch root branch))) (cond ((null br) ;; Data not in tree, insert it. (setf (avl-tree--node-branch root branch) (avl-tree--node-create nil nil data 0)) - t) + (cons t data)) ((funcall cmpfun data (avl-tree--node-data br)) - (and (avl-tree--do-enter cmpfun br 0 data) - (avl-tree--enter-balance root branch 0))) + (let ((ret (avl-tree--do-enter cmpfun br 0 data updatefun))) + (cons (and (car ret) (avl-tree--enter-balance root branch 0)) + (cdr ret)))) ((funcall cmpfun (avl-tree--node-data br) data) - (and (avl-tree--do-enter cmpfun br 1 data) - (avl-tree--enter-balance root branch 1))) + (let ((ret (avl-tree--do-enter cmpfun br 1 data updatefun))) + (cons (and (car ret) (avl-tree--enter-balance root branch 1)) + (cdr ret)))) + ;; Data already in tree, update it. (t - (setf (avl-tree--node-data br) data) - nil)))) + (let ((newdata + (if updatefun + (funcall updatefun data (avl-tree--node-data br)) + data))) + (if (or (funcall cmpfun newdata data) + (funcall cmpfun data newdata)) + (error "avl-tree-enter:\ + updated data does not match existing data")) + (setf (avl-tree--node-data br) newdata) + (cons nil newdata)) ; return value + )))) + ;; ---------------------------------------------------------------- @@ -357,6 +392,30 @@ (avl-tree--node-data root) (avl-tree--node-balance root)))) +(defstruct (avl-tree--stack + (:constructor nil) + (:constructor avl-tree--stack-create + (tree &optional reverse + &aux + (store + (if (avl-tree-empty tree) + nil + (list (avl-tree--root tree)))))) + (:copier nil)) + reverse store) + +(defalias 'avl-tree-stack-p 'avl-tree--stack-p + "Return t if argument is an avl-tree-stack, nil otherwise.") + +(defun avl-tree--stack-repopulate (stack) + ;; Recursively push children of the node at the head of STACK onto the + ;; front of the STACK, until a leaf is reached. + (let ((node (car (avl-tree--stack-store stack))) + (dir (if (avl-tree--stack-reverse stack) 1 0))) + (when node ; check for emtpy stack + (while (setq node (avl-tree--node-branch node dir)) + (push node (avl-tree--stack-store stack)))))) + ;; ================================================================ ;;; The public functions which operate on AVL trees. @@ -375,30 +434,56 @@ "Return t if avl tree TREE is emtpy, otherwise return nil." (null (avl-tree--root tree))) -(defun avl-tree-enter (tree data) - "In the avl tree TREE insert DATA. -Return DATA." - (avl-tree--do-enter (avl-tree--cmpfun tree) - (avl-tree--dummyroot tree) - 0 - data) - data) - -(defun avl-tree-delete (tree data) - "From the avl tree TREE, delete DATA. -Return the element in TREE which matched DATA, -nil if no element matched." - (avl-tree--do-delete (avl-tree--cmpfun tree) - (avl-tree--dummyroot tree) - 0 - data)) +(defun avl-tree-enter (tree data &optional updatefun) + "Insert DATA into the avl tree TREE. + +If an element that matches DATA (according to the tree's +comparison function, see `avl-tree-create') already exists in +TREE, it will be replaced by DATA by default. + +If UPDATEFUN is supplied and an element matching DATA already +exists in TREE, UPDATEFUN is called with two arguments: DATA, and +the matching element. Its return value replaces the existing +element. This value *must* itself match DATA (and hence the +pre-existing data), or an error will occur. + +Returns the new data." + (cdr (avl-tree--do-enter (avl-tree--cmpfun tree) + (avl-tree--dummyroot tree) + 0 data updatefun))) + +(defun avl-tree-delete (tree data &optional test nilflag) + "Delete the element matching DATA from the avl tree TREE. +Matching uses the comparison function previously specified in +`avl-tree-create' when TREE was created. + +Returns the deleted element, or nil if no matching element was +found. + +Optional argument NILFLAG specifies a value to return instead of +nil if nothing was deleted, so that this case can be +distinguished from the case of a successfully deleted null +element. + +If supplied, TEST specifies a test that a matching element must +pass before it is deleted. If a matching element is found, it is +passed as an argument to TEST, and is deleted only if the return +value is non-nil." + (cdr (avl-tree--do-delete (avl-tree--cmpfun tree) + (avl-tree--dummyroot tree) + 0 data test nilflag))) -(defun avl-tree-member (tree data) + +(defun avl-tree-member (tree data &optional nilflag) "Return the element in the avl tree TREE which matches DATA. -Matching uses the compare function previously specified in +Matching uses the comparison function previously specified in `avl-tree-create' when TREE was created. -If there is no such element in the tree, the value is nil." +If there is no such element in the tree, nil is +returned. Optional argument NILFLAG specifies a value to return +instead of nil in this case. This allows non-existent elements to +be distinguished from a null element. (See also +`avl-tree-member-p', which does this for you.)" (let ((node (avl-tree--root tree))) (catch 'found (while node @@ -410,7 +495,16 @@ (avl-tree--node-data node) data) (setq node (avl-tree--node-right node))) (t (throw 'found (avl-tree--node-data node))))) - nil))) + nilflag))) + + +(defun avl-tree-member-p (tree data) + "Return t if an element matching DATA exists in the avl tree TREE, +otherwise return nil. Matching uses the comparison function +previously specified in `avl-tree-create' when TREE was created." + (let ((flag '(nil))) + (not (eq (avl-tree-member tree data flag) flag)))) + (defun avl-tree-map (__map-function__ tree &optional reverse) "Modify all elements in the avl tree TREE by applying FUNCTION. @@ -427,6 +521,57 @@ (avl-tree--root tree) (if reverse 1 0))) + +(defun avl-tree-mapc (__map-function__ tree &optional reverse) + "Apply FUNCTION to all elements in avl tree TREE, +for side-effect only. + +FUNCTION is applied to the elements in ascending order, or +descending order if REVERSE is non-nil." + (avl-tree--mapc + (lambda (node) + (funcall __map-function__ (avl-tree--node-data node))) + (avl-tree--root tree) + (if reverse 1 0))) + + +(defun avl-tree-mapf + (__map-function__ combinator tree &optional reverse) + "Apply FUNCTION to all elements in avl tree TREE, +and combine the results using COMBINATOR. + +The FUNCTION is applied and the results are combined in ascending +order, or descending order if REVERSE is non-nil." + (let (avl-tree-mapf--accumulate) + (avl-tree--mapc + (lambda (node) + (setq avl-tree-mapf--accumulate + (funcall combinator + (funcall __map-function__ + (avl-tree--node-data node)) + avl-tree-mapf--accumulate))) + (avl-tree--root tree) + (if reverse 0 1)) + (nreverse avl-tree-mapf--accumulate))) + + +(defun avl-tree-mapcar (__map-function__ tree &optional reverse) + "Apply FUNCTION to all elements in avl tree TREE, +and make a list of the results. + +The FUNCTION is applied and the list constructed in ascending +order, or descending order if REVERSE is non-nil. + +Note that if you don't care about the order in which FUNCTION is +applied, just that the resulting list is in the correct order, +then + + (avl-tree-mapf function 'cons tree (not reverse)) + +is more efficient." + (nreverse (avl-tree-mapf __map-function__ 'cons tree reverse))) + + (defun avl-tree-first (tree) "Return the first element in TREE, or nil if TREE is empty." (let ((node (avl-tree--root tree))) @@ -469,6 +614,65 @@ "Clear the avl tree TREE." (setf (avl-tree--root tree) nil)) + +(defun avl-tree-stack (tree &optional reverse) + "Return an object that behaves like a sorted stack +of all elements of TREE. + +If REVERSE is non-nil, the stack is sorted in reverse order. +\(See also `avl-tree-stack-pop'\). + +Note that any modification to TREE *immediately* invalidates all +avl-tree-stacks created before the modification (in particular, +calling `avl-tree-stack-pop' will give unpredictable results). + +Operations on these objects are significantly more efficient than +constructing a real stack with `avl-tree-flatten' and using +standard stack functions. As such, they can be useful in +implementing efficient algorithms of AVL trees. However, in cases +where mapping functions `avl-tree-mapc', `avl-tree-mapcar' or +`avl-tree-mapf' would be sufficient, it is better to use one of +those instead." + (let ((stack (avl-tree--stack-create tree reverse))) + (avl-tree--stack-repopulate stack) + stack)) + + +(defun avl-tree-stack-pop (avl-tree-stack &optional nilflag) + "Pop the first element from AVL-TREE-STACK. +\(See also `avl-tree-stack'\). + +Returns nil if the stack is empty, or NILFLAG if specified. (The +latter allows an empty stack to be distinguished from a null +element stored in the AVL tree.)" + (let (node next) + (if (not (setq node (pop (avl-tree--stack-store avl-tree-stack)))) + nilflag + (when (setq next + (avl-tree--node-branch + node + (if (avl-tree--stack-reverse avl-tree-stack) 0 1))) + (push next (avl-tree--stack-store avl-tree-stack)) + (avl-tree--stack-repopulate avl-tree-stack)) + (avl-tree--node-data node)))) + + +(defun avl-tree-stack-first (avl-tree-stack &optional nilflag) + "Return the first element of AVL-TREE-STACK, without removing it +from the stack. + +Returns nil if the stack is empty, or NILFLAG if specified. (The +latter allows an empty stack to be distinguished from a null +element stored in the AVL tree.)" + (or (car (avl-tree--stack-store avl-tree-stack)) + nilflag)) + + +(defun avl-tree-stack-empty-p (avl-tree-stack) + "Return t if AVL-TREE-STACK is empty, nil otherwise." + (null (avl-tree--stack-store avl-tree-stack))) + + (provide 'avl-tree) ;; arch-tag: 47e26701-43c9-4222-bd79-739eac6357a9