;;; b-tree.scm - a B-tree for Xanadu
;;;
;;; Copyright (c) 2012 Johan Ceuppens
;;;
;;; All rights reserved.
;;;
;;; Redistribution and use in source and binary forms, with or without
;;; modification, are permitted provided that the following conditions
;;; are met:
;;; 1. Redistributions of source code must retain the above copyright
;;; notice, this list of conditions and the following disclaimer.
;;; 2. Redistributions in binary form must reproduce the above copyright
;;; notice, this list of conditions and the following disclaimer in the
;;; documentation and/or other materials provided with the distribution.
;;; 3. The name of the authors may not be used to endorse or promote products
;;; derived from this software without specific prior written permission.
;;;
;;; THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
;;; IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
;;; OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
;;; IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT,
;;; INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
;;; NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
;;; DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
;;; THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
;;; (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
;;; THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
;; FIXMES
;; copy vector nodes into n-ary vectors (from median splitted vecs)
(define (make-b-tree-node l r)
(let ((data #f)
(left l)
(right r))
(define (get-data)
data)
(define (set-data! value)
(set! data value))
(define (set-left-with-index! i value)
(cond ((not left)
(display "b-tree : no left node vector.")
#f)
(else (vector-set! left i value))))
(define (set-right-with-index! i value)
(cond ((not right)
(display "b-tree : no right node vector")
#f)
(else (vector-set! right i value))))
(define (get-left)
left)
(define (get-right)
right)
(define (dispatch msg)
(lambda (msg)
(cond ((eq? msg 'get-left)
get-left)
((eq? msg 'get-right)
get-right)
((eq? msg 'set-left-with-index!)
set-left-with-index!)
((eq? msg 'set-right-with-index!)
set-right-with-index!)
((eq? msg 'get-data)
get-data)
((eq? msg 'set-data!)
set-data!)
(else (display "b-tree-node : message not understood")(newline)))))
dispatch))
(define (make-b-tree n-ary)
(let ((*tree (make-b-tree-node
(make-vector n-ary (make-b-tree-node #f #f))
(make-vector n-ary (make-b-tree-node #f #f)))))
(define (vector-median v)
(let ((len (ceiling (/ (vector-length v) 2))))
(let ((retl (make-vector len (make-b-tree-node #f #f)))
(retr (if (odd? len)
(make-vector (+ len 1) (make-b-tree-node #f #f))
(make-vector len (make-b-tree-node #f #f)))))
(do ((i 0 (+ i 1)))
((= i len)(list retl retr))
(vector-set! retl i (vector-ref v i))
(vector-set! retr (- len (+ i 1)) (vector-ref v (- len (+ i 1))))
))))
(define (search-rec str tree side-string) ;; root param in b-treenode
(let* ((side-tree (tree side-string))
(len (vector-length side-tree)))
(do ((i 0 (+ i 1)))
((let* ((side-tree-el-first (vector-ref side-tree i)))
(cond ((>= i len);;last node
(do ((j 0 (+ j 1)))
((= j len) 0)
(search-rec str (vector-ref side-tree j))))
((let ((side-tree-el-second ((vector-ref side-tree (+ i 1)))))
(and (string<? str
((side-tree-el-first 'get-data)))
(string>? str
((side-tree-el-second 'get-data))))
(display "b-tree search : node not found in tree.") 0))
((string=? str ((side-tree-el-first 'get-data)))
(display "b-tree search : string found in tree.") str)
(else (display "b-tree : never reached."))))))))
(define (search str)
(search-rec str *tree 'get-left)
(search-rec str *tree 'get-right))
(define (dump-rec tree) ;; root param in b-treenode
(if (not (tree 'get-left))
0
(let ((len (vector-length (tree 'get-left))))
(do ((i 0 (+ i 1)))
((>= i len) 0)
(display (((vector-ref (tree 'get-left) i)'get-data)))
(dump-rec (vector-ref (tree 'get-left) i))
)))
(if (not (tree 'get-right))
0
(let ((len (vector-length (tree 'get-right))))
(do ((i 0 (+ i 1)))
((>= i len) 0)
(dump-rec (vector-ref (tree 'get-right) i))
))))
(define (dump)
(dump-rec *tree))
(define (add-rec str tree) ;; root param in b-treenode ;; refactor call-with-values
(let ((lefttree (tree 'get-left));;FIXME ()
(righttree (tree 'get-right)))
;;len (vector-length ((tree 'get-left)))))
;;(call-with-values
;; (lambda () (values lefttree righttree))
;; (lambda (lefttree righttree)
(add-rec-side-tree str lefttree)
(add-rec-side-tree str righttree)
;; ))
))
(define (add-rec-side-tree str side-tree)
(do ((i 0 (+ i 1)))
((cond ((not side-tree)
#f)
((let* ((data (((vector-ref side-tree i) 'get-data)))
(left-and-right (vector-median side-tree));;FIXME right also descend
(new-node (make-b-tree-node
(car left-and-right)
(cadr left-and-right))));;FIXME lenght mustbe n-ary
(or data (and (string? data)(string=? data "")))
((new-node 'set-data!) str)
;;((side-tree 'set-left-with-index!) i new-node)
(vector-set! side-tree i new-node)
(set! i (vector-length side-tree))))
((let ((data (((vector-ref side-tree i) 'get-data))))
(or ;;(and (string=?)
;; (string>? str data))
(and (string? data)
(string=? data ""))
(and (string? data)
(string<? str data)
(string>? str data)))
(let ((left-and-right (vector-median side-tree)))
(let ((new-node (make-b-tree-node (car left-and-right) (cadr left-and-right))))
((new-node 'set-data!) str)
(vector-set! side-tree i new-node)
))))
;;((= i len)
;; (display "node not added .") 0)
(else (display "b-tree add - never reached.")))))
(do ((i 0 (+ i 1)))
((= i (vector-length side-tree))0)
(let ((side-tree-node (vector-ref i side-tree)))
(cond ((not (not side-tree-node))
#f)
(else (add-rec str side-tree-node)))));;NOTE add-rec not the other add-rec
)
(define (add str)
(add-rec str *tree)
)
(define (dispatch msg)
(cond ((eq? msg 'add) add)
((eq? msg 'search) search)
((eq? msg 'dump) dump)
(else (display "b-tree : message not understood.")(newline))))
dispatch))
;; test program
;;(define bt (make-b-tree 2))
;;((bt 'add)"abc")
;;((bt 'add)"def")
;;((bt 'add)"hij")
;;((bt 'search)"abc")
;;((bt 'dump))