208 lines
7.8 KiB
Scheme
208 lines
7.8 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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;; FIXME
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;; use lets for vectorrefs etc.
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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 ((numitems 0)
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(numnodes 0)
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(root 'foo)
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(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 "not left"))
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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 "not right"))
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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 (get-root)
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root)
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(define (get-numitems)
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numitems)
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(define (get-numnodes)
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numnodes)
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(define (dispatch msg)
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(lambda (msg)
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(cond ((eq? msg 'get-root)
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get-root)
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((eq? msg 'get-numitems)
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get-numitems)
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((eq? msg 'get-numnodes)
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get-numnodes)
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((eq? msg 'get-left)
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get-left)
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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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((eq? msg 'get-right)
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get-right)
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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);;NOTE FIXME n-ary and vector-length
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(let ((*tree (make-b-tree-node;; #f #f)))
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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 v)
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(let ((len (ceiling (/ (vector-length v) 2))))
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(let ((retl (make-vector len (make-b-tree-node #f #f)))
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(retr (if (odd? len)
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(make-vector (+ len 1) (make-b-tree-node #f #f))
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(make-vector len (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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(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 lefttree)))
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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 1);;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 j side-tree))))
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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 "node not found in tree.") 0))
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((string=? str ((side-tree-el-first 'get-data)))
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(display "string found in tree.") str)
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(else (display "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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(define (dump-rec tree) ;; root param in b-treenode
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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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(do ((i 0 (+ i 1)))
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((cond ((or lefttree
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(not (((vector-ref lefttree i) 'get-data)))
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(string=? (((vector-ref lefttree i) 'get-data)) ""))
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(let ((lr (vector-median ((lefttree 'get-left)))));;FIXME right also descend
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(let ((new-node (make-b-tree-node (car lr) (cadr lr))));;FIXME lenght mustbe n-ary
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((new-node 'set-data!) str)
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((lefttree 'set-left-with-index!) i new-node)
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)))
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((and (string<? str (((vector-ref lefttree i) 'get-data)))
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(string>? str (((vector-ref lefttree (+ i 1)) 'get-data))))
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(let ((lr (vector-median ((lefttree 'get-left)))))
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(let ((new-node (make-b-tree-node (car lr) (cadr lr))))
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((new-node 'set-data!) str)
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(vector-set! lefttree i new-node)
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)))
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;;((string=? str (((vector-ref lefttree i)'get-data)))
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;; (set! i (vector-length tree)))
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((>= i (- len 1));;last node
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(do ((j 0 (+ j 1)))
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((= j len) (display "node not added.") 0)
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(add-rec str (vector-ref lefttree i)))
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)
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(else (display "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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(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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