/usr/share/gauche-0.9/0.9.1/lib/util/lcs.scm is in gauche 0.9.1-5.
This file is owned by root:root, with mode 0o644.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 | ;;;; lcs.scm -- find out the longest common sequence
;;;
;;; Copyright (c) 2002-2003 by Alex Shinn, All rights reserved.
;;; Copyright (c) 2002-2010 Shiro Kawai <shiro@acm.org>
;;;
;;; 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. Neither the name of the authors nor the names of its contributors
;;; may be used to endorse or promote products derived from this
;;; software without specific prior written permission.
;;;
;;; THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
;;; "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 COPYRIGHT
;;; OWNER OR CONTRIBUTORS 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
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;;;
;;; Created: <2002-06-21 15:36:46 foof>
;;; Time-stamp: <2003-02-15 00:09:55 foof>
;;; Author: Alex Shinn <foof@synthcode.com>
;;; Modified by Shiro Kawai
;;; - added lcs-fold and rewrote lcs-edit-list using lcs-fold
;;; - replaced base algorithm from DP to Myers'
(define-module util.lcs
(use gauche.sequence)
(use srfi-1)
(use srfi-11)
(export lcs lcs-with-positions lcs-fold lcs-edit-list))
(select-module util.lcs)
;; The base algorithm. This code implements
;; Eugene Myers, "An O(ND) Difference Algorithm and Its Variations",
;; Algorithmica Vol. 1 No. 2, 1986, pp. 251-266.
;; It takes O((M+N)D) time and O((M+N)L) space, where
;; N = (length a), M = (length b), D is the length of the smallest edit
;; sequence (SES), and L is the length of the longest common subsequence (LCS).
;; In most applications the difference is small, so it is much better than
;; DP algorithm that is generally O(MN) time and space complextiy.
;; The worst case where a and b totally differ is O((M+N)^2).
;; The Myers's paper gives refinement of the algorithm
;; that improves worst case behavior, but I don't implement it yet. --[SK]
(define (lcs-with-positions a-ls b-ls . opt-eq)
(let* ((eq (get-optional opt-eq equal?))
(A (list->vector a-ls))
(B (list->vector b-ls))
(N (vector-length A))
(M (vector-length B))
(M+N (+ N M))
(V_d (make-vector (+ (* 2 M+N) 1) 0))
(V_r (make-vector (+ (* 2 M+N) 1) '()))
(V_l (make-vector (+ (* 2 M+N) 1) 0)))
(let-syntax ((vd
(syntax-rules ()
((vd i) (vector-ref V_d (+ i M+N)))
((vd i x) (vector-set! V_d (+ i M+N) x))))
(vr
(syntax-rules ()
((vr i) (vector-ref V_r (+ i M+N)))
((vr i x) (vector-set! V_r (+ i M+N) x))))
(vl
(syntax-rules ()
((vl i) (vector-ref V_l (+ i M+N)))
((vl i x) (vector-set! V_l (+ i M+N) x)))))
(define (finish)
(let loop ((i (- M+N)) (maxl 0) (r '()))
(cond ((> i M+N) (list maxl (reverse! r)))
((> (vl i) maxl)
(loop (+ i 1) (vl i) (vr i)))
(else
(loop (+ i 1) maxl r)))))
(if (zero? M+N)
'(0 ()) ;; boundary case
(let d-loop ((d 0))
(if (> d M+N)
(error "lcs-with-positions; something's wrong (implementation error?)")
(let k-loop ((k (- d)))
(if (> k d)
(d-loop (+ d 1))
(receive (x l r)
(if (or (= k (- d))
(and (not (= k d))
(< (vd (- k 1)) (vd (+ k 1)))))
(values (vd (+ k 1)) (vl (+ k 1)) (vr (+ k 1)))
(values (+ (vd (- k 1)) 1) (vl (- k 1)) (vr (- k 1))))
(receive (x y l r)
(let xy-loop ((x x) (y (- x k)) (l l) (r r))
(cond ((>= x N) (values x y l r))
((>= y M) (values x y l r))
((eq (vector-ref A x) (vector-ref B y))
(xy-loop (+ x 1) (+ y 1) (+ l 1)
(cons (list (vector-ref A x) x y)
r)))
(else (values x y l r))))
(vd k x)
(vr k r)
(vl k l)
(if (and (>= x N) (>= y M))
(finish)
(k-loop (+ k 2))))
)))
)))
)))
;; Just returns the LCS
(define (lcs a b . opt-eq)
(map car (cadr (lcs-with-positions a b (get-optional opt-eq equal?)))))
;; Fundamental iterator to deal with editlist.
;; Similar to Perl's Algorith::Diff's traverse_sequence.
(define (lcs-fold a-only b-only both seed a b . opt-eq)
(let1 common (cadr (lcs-with-positions a b (get-optional opt-eq equal?)))
;; Calculates edit-list from the LCS.
;; Loop parameters:
;; common - list of common elements
;; seed - seed value
;; a - head of sequence a
;; a-pos - current position count of sequence a
;; b - head of sequence b
;; b-pos - current position count of sequence b
(let loop ((common common) (seed seed)
(a a) (a-pos 0) (b b) (b-pos 0))
(if (null? common)
;; No more common elements. Fold the tail of a and b.
(fold b-only (fold a-only seed a) b)
;; We have a common element.
(let* ((elt (car common))
(a-off (cadr elt))
(a-skip (- a-off a-pos))
(b-off (caddr elt))
(b-skip (- b-off b-pos)))
(let-values (((a-head a-tail) (split-at a a-skip))
((b-head b-tail) (split-at b b-skip)))
(loop (cdr common)
(both (car elt)
(fold b-only (fold a-only seed a-head) b-head))
(cdr a-tail) (+ a-off 1) (cdr b-tail) (+ b-off 1)))))
)
))
;; Returns an 'edit-list', which is a list of command sequences
;; that turns the sequence a to the sequence b.
;; The return value is a list of hunks, where each hunk is a
;; list of edit commands, (<command> <index> <element>).
(define (lcs-edit-list a b . opt-eq)
(define a-pos -1) ;; we use pre-increment, so begin from -1.
(define b-pos -1) ;; ditto
(define hunks '())
(let1 last
(apply lcs-fold
(lambda (elt hunk) ;; a-only - remove
(inc! a-pos) `((- ,a-pos ,elt) ,@hunk))
(lambda (elt hunk) ;; b-only - add
(inc! b-pos) `((+ ,b-pos ,elt) ,@hunk))
(lambda (elt hunk) ;; same - reset hunks
(inc! a-pos) (inc! b-pos)
(unless (null? hunk) (push! hunks (reverse! hunk)))
'())
'()
a b opt-eq)
(unless (null? last) (push! hunks (reverse! last))))
(reverse! hunks))
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