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=begin pod | ||
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This is a direct port of the Perl 5 version and should be close to 100% similar | ||
other then some Perl 6 idioms. I didn't port the fastdistance routine since the | ||
logic was buggy and the code to fix it made it the same speed as the regular | ||
distance routine. | ||
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=head1 NAME | ||
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Text::Levenshtein - An implementation of the Levenshtein edit distance | ||
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=head1 SYNOPSIS | ||
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use Text::Levenshtein qw(distance); | ||
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print distance("foo","four"); | ||
# prints "2" | ||
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my @words=("four","foo","bar"); | ||
my @distances=distance("foo",@words); | ||
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print "@distances"; | ||
# prints "2 0 3" | ||
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=head1 DESCRIPTION | ||
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This module implements the Levenshtein edit distance. The Levenshtein edit | ||
distance is a measure of the degree of proximity between two strings. This | ||
distance is the number of substitutions, deletions or insertions ("edits") | ||
needed to transform one string into the other one (and vice versa). When two | ||
strings have distance 0, they are the same. A good point to start is: | ||
L< http://www.merriampark.com/ld.htm > | ||
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=head1 AUTHOR | ||
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Copyright 2002 Dree Mistrut <F<dree@friul.it>> | ||
perl6 port: 2010 Steve Schulze aka thundergnat | ||
L< http://perlmonks.org/?node=thundergnat > | ||
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This package is free software and is provided "as is" without express or implied | ||
warranty. You can redistribute it and/or modify it under the same terms as Perl | ||
itself. | ||
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=end pod |
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module Text::Levenshtein; | ||
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sub _min | ||
{ | ||
return $^a < $^b | ||
?? $^a < $^c ?? $^a !! $^c | ||
!! $^b < $^c ?? $^b !! $^c; | ||
} | ||
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sub distance ($s, *@t) is export | ||
{ | ||
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my $n = $s.chars; | ||
my @result; | ||
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for (@t) -> $t { | ||
if ($s eq $t) { | ||
push @result, 0; | ||
next; | ||
} | ||
my @d; | ||
my $cost=0; | ||
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my $m = $t.chars; | ||
@result.push($m) and next unless $n; | ||
@result.push($n) and next unless $m; | ||
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@d[0][0] = 0; | ||
for (1 .. $n) -> $i { | ||
@d[$i][0] = $i; | ||
} | ||
for (1 .. $m) -> $j { | ||
@d[0][$j] = $j; | ||
} | ||
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for (1 .. $n) -> $i { | ||
my $s_i = $s.substr($i-1,1); | ||
for (1 .. $m) -> $j { | ||
@d[$i][$j] = | ||
_min(@d[$i-1][$j]+1, @d[$i][$j-1]+1, | ||
@d[$i-1][$j-1]+($s_i eq substr($t,$j-1,1) ?? 0 !! 1) ) | ||
} | ||
} | ||
push @result,@d[$n][$m]; | ||
} | ||
return @result; | ||
} | ||
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=begin pod | ||
=head1 NAME | ||
Text::Levenshtein - An implementation of the Levenshtein edit distance | ||
=head1 SYNOPSIS | ||
use Text::Levenshtein qw(distance); | ||
print distance("foo","four"); | ||
# prints "2" | ||
my @words=("four","foo","bar"); | ||
my @distances=distance("foo",@words); | ||
print "@distances"; | ||
# prints "2 0 3" | ||
=head1 DESCRIPTION | ||
This module implements the Levenshtein edit distance. | ||
The Levenshtein edit distance is a measure of the degree of proximity between two strings. | ||
This distance is the number of substitutions, deletions or insertions ("edits") | ||
needed to transform one string into the other one (and vice versa). | ||
When two strings have distance 0, they are the same. | ||
A good point to start is: <http://www.merriampark.com/ld.htm> | ||
#See also Text::LevenshteinXS on CPAN if you do not require a perl-only implementation. It | ||
#is extremely faster in nearly all cases. | ||
#See also Text::WagnerFischer on CPAN for a configurable edit distance, i.e. for | ||
#configurable costs (weights) for the edits. | ||
=head1 AUTHOR | ||
Copyright 2002 Dree Mistrut <F<dree@friul.it>> | ||
perl6 port: 2010 Steve Schulze | ||
This package is free software and is provided "as is" without express | ||
or implied warranty. You can redistribute it and/or modify it under | ||
the same terms as Perl itself. | ||
=end pod | ||
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use Test; | ||
plan 9; | ||
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use Text::Levenshtein; | ||
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is(distance("foo","four"),2,"Correct distance foo four"); | ||
is(distance("foo","foo"),0,"Correct distance foo foo"); | ||
is(distance("cow","cat"),2,"Correct distance cow cat"); | ||
is(distance("cat","moocow"),5,"Correct distance cat moocow"); | ||
is(distance("cat","cowmoo"),5,"Correct distance cat cowmoo"); | ||
is(distance("cow","moocow"),3,"Correct distance cow moocow"); | ||
is(distance("sebastian","sebastien"),1,"Correct distance sebastian sebastien"); | ||
is(distance("more","cowbell"),5,"Correct distance more cowbell"); | ||
my @foo = distance("foo","four","foo","bar"); | ||
my @bar = (2,0,3); | ||
is(@foo,@bar,"Array test: Correct distances foo four foo bar"); | ||
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