223 lines
8.7 KiB
Scheme
223 lines
8.7 KiB
Scheme
;;; b-tree.scm - a B-tree for Xanadu
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;;;
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;;; Copyright (c) 2012 Johan Ceuppens
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;;;
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;;; All rights reserved.
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;;;
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;;; Redistribution and use in source and binary forms, with or without
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;;; modification, are permitted provided that the following conditions
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;;; are met:
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;;; 1. Redistributions of source code must retain the above copyright
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;;; notice, this list of conditions and the following disclaimer.
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;;; 2. Redistributions in binary form must reproduce the above copyright
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;;; notice, this list of conditions and the following disclaimer in the
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;;; documentation and/or other materials provided with the distribution.
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;;; 3. The name of the authors may not be used to endorse or promote products
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;;; derived from this software without specific prior written permission.
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;;;
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;;; THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR
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;;; IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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;;; OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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;;; IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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;;; INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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;;; NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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;;; DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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;;; THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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;;; (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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;;; THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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;; FIXMES
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;; copy vector nodes into n-ary vectors (from median splitted vecs)
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(define (make-b-tree-node l r)
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(let ((data #f)
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(left l)
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(right r))
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(define (get-data)
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data)
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(define (set-data! value)
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(set! data value))
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(define (set-left-with-index! i value)
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(cond ((not left)
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(display "b-tree : no left node vector.")
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#f)
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(else (vector-set! left i value))))
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(define (set-right-with-index! i value)
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(cond ((not right)
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(display "b-tree : no right node vector")
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#f)
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(else (vector-set! right i value))))
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(define (get-left)
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left)
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(define (get-right)
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right)
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(define (dispatch msg)
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(lambda (msg)
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(cond ((eq? msg 'get-left)
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get-left)
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((eq? msg 'get-right)
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get-right)
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((eq? msg 'set-left-with-index!)
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set-left-with-index!)
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((eq? msg 'set-right-with-index!)
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set-right-with-index!)
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((eq? msg 'get-data)
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get-data)
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((eq? msg 'set-data!)
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set-data!)
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(else (display "b-tree-node : message not understood")(newline)))))
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dispatch))
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(define (make-b-tree n-ary)
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(let ((*tree (make-b-tree-node
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(make-vector n-ary (make-b-tree-node #f #f))
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(make-vector n-ary (make-b-tree-node #f #f)))))
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(define (vector-median j v)
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(let ((len (vector-length v)))
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(let ((retl (make-vector (- j 1) (make-b-tree-node #f #f)))
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(retr (make-vector (- len (+ j 1)) (make-b-tree-node #f #f))))
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(do ((i 0 (+ i 1)))
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((= i len)(list retl retr))
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(vector-set! retl i (vector-ref v i))
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(vector-set! retr (- len (+ i 1)) (vector-ref v (- len (+ i 1))))
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))))
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;;FIXME
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(define (search-rec str tree side-string) ;; root param in b-treenode
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(let* ((side-tree (tree side-string))
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(len (vector-length side-tree)))
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(do ((i 0 (+ i 1)))
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((let ((side-tree-el-first (vector-ref side-tree i)))
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(cond ((>= i len);;last node
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(do ((j 0 (+ j 1)))
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((= j len) 0)
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(search-rec str (vector-ref side-tree j) 'get-left)
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(search-rec str (vector-ref side-tree j) 'get-right)
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))
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((let ((side-tree-el-second (vector-ref side-tree (+ i 1))))
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(and (string<? str
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((side-tree-el-first 'get-data)))
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(string>? str
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((side-tree-el-second 'get-data))))
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(display "b-tree search : node not found in tree.") 0))
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((string=? str ((side-tree-el-first 'get-data)))
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(display "b-tree search : string found in tree.") str)
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(else (display "b-tree : never reached."))))))))
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(define (search str)
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(search-rec str *tree 'get-left)
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(search-rec str *tree 'get-right))
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;;FIXME
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(define (dump-rec tree)
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(if (not (tree 'get-left))
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0
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(let ((len (vector-length (tree 'get-left))))
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(do ((i 0 (+ i 1)))
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((>= i len) 0)
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(display (((vector-ref (tree 'get-left) i)'get-data)))
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(dump-rec (vector-ref (tree 'get-left) i))
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)))
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(if (not (tree 'get-right))
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0
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(let ((len (vector-length (tree 'get-right))))
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(do ((i 0 (+ i 1)))
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((>= i len) 0)
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(dump-rec (vector-ref (tree 'get-right) i))
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))))
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(define (dump)
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(dump-rec *tree))
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(define (add-rec str tree) ;; root param in b-treenode ;; refactor call-with-values
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(let ((lefttree (tree 'get-left));;FIXME ()
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(righttree (tree 'get-right)))
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;;len (vector-length ((tree 'get-left)))))
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;;(call-with-values
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;; (lambda () (values lefttree righttree))
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;; (lambda (lefttree righttree)
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(add-rec-side-tree str lefttree)
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(add-rec-side-tree str righttree)
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;; ))
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))
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(define (add-rec-side-tree str side-tree)
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(do ((i 0 (+ i 1)))
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((cond ((not side-tree)
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#f)
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((= i (vector-length side-tree))
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(do ((i 0 (+ i 1)))
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((= i (vector-length side-tree))0)
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(let ((side-tree-node (vector-ref i side-tree)))
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(cond ((not (not side-tree-node))
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#f)
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(else (add-rec str side-tree-node)))));;NOTE add-rec not the other add-rec
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)
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((let* ((data (((vector-ref side-tree i) 'get-data)))
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(left-and-right (vector-median i side-tree));;FIXME right also descend
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(new-node (make-b-tree-node
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(car left-and-right)
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(cadr left-and-right))));;FIXME lenght mustbe n-ary
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(or (not data)
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(and data (string? data)(string=? data "")))
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((new-node 'set-data!) str)
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;;((side-tree 'set-left-with-index!) i new-node)
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(vector-set! side-tree i new-node)
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(set! i (vector-length side-tree))))
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((let ((data (((vector-ref side-tree i) 'get-data)))
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(data2 (((vector-ref side-tree (if (< (- i 1)(vector-length side-tree))
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(+ i 1)
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i)
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) 'get-data))))
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(or ;;(and (string=?)
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;; (string>? str data))
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(and (string? data)
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(string=? data ""))
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(and (string? data)
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(string? data2)
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(string<? str data)
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(string>? str data2)));;FIXME data2!
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(let ((left-and-right (vector-median i side-tree)))
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(let ((new-node (make-b-tree-node (car left-and-right) (cadr left-and-right))))
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((new-node 'set-data!) str)
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(vector-set! side-tree i new-node)
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))))
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((let ((data (((vector-ref side-tree i) 'get-data))))
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(string=? data str) ;;NOTE duplicates possible
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(display "b-tree - node already exists.")
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0))
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(else (display "b-tree - add - never reached.")))))
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)
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(define (add str)
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(add-rec str *tree)
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)
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(define (dispatch msg)
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(cond ((eq? msg 'add) add)
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((eq? msg 'search) search)
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((eq? msg 'dump) dump)
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(else (display "b-tree : message not understood.")(newline))))
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dispatch))
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;; test program
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;;(define bt (make-b-tree 2))
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;;((bt 'add)"abc")
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;;((bt 'add)"def")
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;;((bt 'add)"hij")
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;;((bt 'search)"abc")
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;;((bt 'dump))
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