307 lines
7.9 KiB
Perl
307 lines
7.9 KiB
Perl
# This is a version of Algorithm::Diff that uses only a comparison function,
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# like versions <= 0.59 used to.
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# $Revision: 1.3 $
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package # don't index
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Algorithm::DiffOld;
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use strict;
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use vars qw($VERSION @EXPORT_OK @ISA @EXPORT);
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use integer; # see below in _replaceNextLargerWith() for mod to make
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# if you don't use this
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require Exporter;
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@ISA = qw(Exporter);
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@EXPORT = qw();
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@EXPORT_OK = qw(LCS diff traverse_sequences);
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$VERSION = 1.10; # manually tracking Algorithm::Diff
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# McIlroy-Hunt diff algorithm
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# Adapted from the Smalltalk code of Mario I. Wolczko, <mario@wolczko.com>
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# by Ned Konz, perl@bike-nomad.com
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=head1 NAME
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Algorithm::DiffOld - Compute `intelligent' differences between two files / lists
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but use the old (<=0.59) interface.
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=head1 NOTE
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This has been provided as part of the Algorithm::Diff package by Ned Konz.
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This particular module is B<ONLY> for people who B<HAVE> to have the old
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interface, which uses a comparison function rather than a key generating
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function.
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Because each of the lines in one array have to be compared with each
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of the lines in the other array, this does M*N comparisons. This can
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be very slow. I clocked it at taking 18 times as long as the stock
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version of Algorithm::Diff for a 4000-line file. It will get worse
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quadratically as array sizes increase.
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=head1 SYNOPSIS
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use Algorithm::DiffOld qw(diff LCS traverse_sequences);
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@lcs = LCS( \@seq1, \@seq2, $comparison_function );
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$lcsref = LCS( \@seq1, \@seq2, $comparison_function );
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@diffs = diff( \@seq1, \@seq2, $comparison_function );
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traverse_sequences( \@seq1, \@seq2,
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{ MATCH => $callback,
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DISCARD_A => $callback,
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DISCARD_B => $callback,
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},
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$comparison_function );
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=head1 COMPARISON FUNCTIONS
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Each of the main routines should be passed a comparison function. If you
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aren't passing one in, B<use Algorithm::Diff instead>.
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These functions should return a true value when two items should compare
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as equal.
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For instance,
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@lcs = LCS( \@seq1, \@seq2, sub { my ($a, $b) = @_; $a eq $b } );
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but if that is all you're doing with your comparison function, just use
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Algorithm::Diff and let it do this (this is its default).
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Or:
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sub someFunkyComparisonFunction
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{
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my ($a, $b) = @_;
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$a =~ m{$b};
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}
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@diffs = diff( \@lines, \@patterns, \&someFunkyComparisonFunction );
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which would allow you to diff an array @lines which consists of text
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lines with an array @patterns which consists of regular expressions.
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This is actually the reason I wrote this version -- there is no way
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to do this with a key generation function as in the stock Algorithm::Diff.
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=cut
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# Find the place at which aValue would normally be inserted into the array. If
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# that place is already occupied by aValue, do nothing, and return undef. If
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# the place does not exist (i.e., it is off the end of the array), add it to
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# the end, otherwise replace the element at that point with aValue.
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# It is assumed that the array's values are numeric.
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# This is where the bulk (75%) of the time is spent in this module, so try to
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# make it fast!
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sub _replaceNextLargerWith
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{
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my ( $array, $aValue, $high ) = @_;
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$high ||= $#$array;
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# off the end?
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if ( $high == -1 || $aValue > $array->[ -1 ] )
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{
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push( @$array, $aValue );
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return $high + 1;
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}
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# binary search for insertion point...
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my $low = 0;
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my $index;
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my $found;
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while ( $low <= $high )
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{
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$index = ( $high + $low ) / 2;
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# $index = int(( $high + $low ) / 2); # without 'use integer'
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$found = $array->[ $index ];
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if ( $aValue == $found )
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{
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return undef;
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}
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elsif ( $aValue > $found )
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{
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$low = $index + 1;
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}
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else
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{
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$high = $index - 1;
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}
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}
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# now insertion point is in $low.
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$array->[ $low ] = $aValue; # overwrite next larger
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return $low;
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}
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# This method computes the longest common subsequence in $a and $b.
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# Result is array or ref, whose contents is such that
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# $a->[ $i ] == $b->[ $result[ $i ] ]
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# foreach $i in ( 0 .. $#result ) if $result[ $i ] is defined.
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# An additional argument may be passed; this is a CODE ref to a comparison
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# routine. By default, comparisons will use "eq" .
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# Note that this routine will be called as many as M*N times, so make it fast!
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# Additional parameters, if any, will be passed to the key generation routine.
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sub _longestCommonSubsequence
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{
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my $a = shift; # array ref
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my $b = shift; # array ref
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my $compare = shift || sub { my $a = shift; my $b = shift; $a eq $b };
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my $aStart = 0;
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my $aFinish = $#$a;
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my $bStart = 0;
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my $bFinish = $#$b;
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my $matchVector = [];
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# First we prune off any common elements at the beginning
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while ( $aStart <= $aFinish
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and $bStart <= $bFinish
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and &$compare( $a->[ $aStart ], $b->[ $bStart ], @_ ) )
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{
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$matchVector->[ $aStart++ ] = $bStart++;
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}
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# now the end
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while ( $aStart <= $aFinish
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and $bStart <= $bFinish
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and &$compare( $a->[ $aFinish ], $b->[ $bFinish ], @_ ) )
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{
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$matchVector->[ $aFinish-- ] = $bFinish--;
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}
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my $thresh = [];
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my $links = [];
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my ( $i, $ai, $j, $k );
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for ( $i = $aStart; $i <= $aFinish; $i++ )
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{
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$k = 0;
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# look for each element of @b between $bStart and $bFinish
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# that matches $a->[ $i ], in reverse order
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for ($j = $bFinish; $j >= $bStart; $j--)
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{
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next if ! &$compare( $a->[$i], $b->[$j], @_ );
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# optimization: most of the time this will be true
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if ( $k
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and $thresh->[ $k ] > $j
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and $thresh->[ $k - 1 ] < $j )
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{
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$thresh->[ $k ] = $j;
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}
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else
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{
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$k = _replaceNextLargerWith( $thresh, $j, $k );
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}
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# oddly, it's faster to always test this (CPU cache?).
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if ( defined( $k ) )
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{
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$links->[ $k ] =
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[ ( $k ? $links->[ $k - 1 ] : undef ), $i, $j ];
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}
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}
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}
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if ( @$thresh )
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{
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for ( my $link = $links->[ $#$thresh ]; $link; $link = $link->[ 0 ] )
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{
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$matchVector->[ $link->[ 1 ] ] = $link->[ 2 ];
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}
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}
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return wantarray ? @$matchVector : $matchVector;
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}
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sub traverse_sequences
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{
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my $a = shift; # array ref
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my $b = shift; # array ref
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my $callbacks = shift || { };
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my $compare = shift;
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my $matchCallback = $callbacks->{'MATCH'} || sub { };
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my $discardACallback = $callbacks->{'DISCARD_A'} || sub { };
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my $finishedACallback = $callbacks->{'A_FINISHED'};
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my $discardBCallback = $callbacks->{'DISCARD_B'} || sub { };
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my $finishedBCallback = $callbacks->{'B_FINISHED'};
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my $matchVector = _longestCommonSubsequence( $a, $b, $compare, @_ );
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# Process all the lines in match vector
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my $lastA = $#$a;
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my $lastB = $#$b;
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my $bi = 0;
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my $ai;
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for ( $ai = 0; $ai <= $#$matchVector; $ai++ )
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{
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my $bLine = $matchVector->[ $ai ];
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if ( defined( $bLine ) ) # matched
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{
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&$discardBCallback( $ai, $bi++, @_ ) while $bi < $bLine;
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&$matchCallback( $ai, $bi++, @_ );
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}
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else
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{
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&$discardACallback( $ai, $bi, @_ );
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}
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}
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# the last entry (if any) processed was a match.
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if ( defined( $finishedBCallback ) && $ai <= $lastA )
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{
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&$finishedBCallback( $bi, @_ );
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}
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else
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{
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&$discardACallback( $ai++, $bi, @_ ) while ( $ai <= $lastA );
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}
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if ( defined( $finishedACallback ) && $bi <= $lastB )
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{
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&$finishedACallback( $ai, @_ );
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}
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else
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{
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&$discardBCallback( $ai, $bi++, @_ ) while ( $bi <= $lastB );
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}
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return 1;
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}
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sub LCS
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{
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my $a = shift; # array ref
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my $matchVector = _longestCommonSubsequence( $a, @_ );
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my @retval;
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my $i;
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for ( $i = 0; $i <= $#$matchVector; $i++ )
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{
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if ( defined( $matchVector->[ $i ] ) )
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{
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push( @retval, $a->[ $i ] );
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}
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}
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return wantarray ? @retval : \@retval;
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}
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sub diff
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{
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my $a = shift; # array ref
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my $b = shift; # array ref
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my $retval = [];
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my $hunk = [];
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my $discard = sub { push( @$hunk, [ '-', $_[ 0 ], $a->[ $_[ 0 ] ] ] ) };
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my $add = sub { push( @$hunk, [ '+', $_[ 1 ], $b->[ $_[ 1 ] ] ] ) };
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my $match = sub { push( @$retval, $hunk ) if scalar(@$hunk); $hunk = [] };
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traverse_sequences( $a, $b,
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{ MATCH => $match, DISCARD_A => $discard, DISCARD_B => $add },
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@_ );
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&$match();
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return wantarray ? @$retval : $retval;
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}
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1;
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