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How do I do a natural sort on an array?

by Anonymous Monk
on Mar 30, 2001 at 00:46 UTC ( #68185=perlquestion: print w/replies, xml ) Need Help??

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question: (sorting)

How do I do a natural sort on an array? i.e. each array element is contains a string made up of numbers and letters.

Originally posted as a Categorized Question.

  • Comment on How do I do a natural sort on an array?

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Re: How do I do a natural sort on an array?
by tye (Sage) on Mar 30, 2001 at 01:15 UTC
    my @sorted= grep {s/(^|\D)0+(\d)/$1$2/g,1} sort grep {s/(\d+)/sprintf"%06.6d",$1/ge,1} @data;
    See RE: RE: Re: Sorting on Section Numbers some important style comments.

    Features and limitations:

    • Strips extra leading zeros from digit strings
    • Doesn't handle floating point numbers at all well
    • Sorts negative integers in reverse after positive integers
    • Uses very little extra memory
    • You must specify the maximum number of digits your integers will have (6 in the above code)
Re: How do I do a natural sort on an array?
by tye (Sage) on Mar 30, 2001 at 01:07 UTC
    my %data; foreach my $data ( @data ) { ( my $sort= $data ) =~ s/(0*)(\d+)/ pack("C",length($2)) . $1 . $2 /ge; $data{$sort}= $data; } my @sorted= @data{ sort keys %data };
    Bugs and features
    • Doesn't properly sort decimal values like 12.34
    • Sorts negative integers in reverse after positive integers
    • Requires more memory than other methods I'll be adding
Re: How do I do a natural sort on an array?
by Dominus (Parson) on Mar 30, 2001 at 19:19 UTC
    I'm not exactly sure what you want (it would have helped if you had provided an example) but here's what I use:
    sub byfile { my @a = split /(\d+)/, $a; my @b = split /(\d+)/, $b; my $M = @a > @b ? @a : @b; my $res = 0; for (my $i = 0; $i < $M; $i++) { return -1 if ! defined $a[$i]; return 1 if ! defined $b[$i]; if ($a[$i] =~ /\d/) { $res = $a[$i] <=> $b[$i]; } else { $res = $a[$i] cmp $b[$i]; } last if $res; } $res; }
    This may be more complicated than you need. Given the following:
    53 7 119 53red red5 red6 red7 red67 red6.jpg red12.jpg green4.jpg blue2.jpg blue1000.jpg blue2.jpg58
    it produces the following output:
    7 53 53red 119 blue2.jpg blue2.jpg58 blue1000.jpg green4.jpg red5 red6 red6.jpg red7 red12.jpg red67
    Lucs St. Louis also suggests:
    while (defined (my $A = shift @a) and defined (my $B = shift @b)) { $res = ($A =~ /\d/) ? $A <=> $B : $A cmp $B; return $res if $res; } return defined $A ? -1 : 1;
    Hope this helps.
Re: How do I do a natural sort on an array?
by salva (Canon) on May 30, 2006 at 10:12 UTC
    Sort::Key::Natural is fast, can handle numbers of unlimited size and doesn't have problems with unicode:
    use Sort::Key::Natural qw(natsort); my @sorted = natsort @data;
Re: How do I do a natural sort on an array?
by indigo (Scribe) on Mar 30, 2001 at 00:53 UTC
    @a = sort @b;

    will sort lexigraphically.

    @a = sort { $a <=> $b } @b;

    will sort numerically.

    @a = sort &naturally @b;

    will sort "naturally", where naturally() is a compare routine of your own devising.

    perldoc -f sort for more info.
Re: How do I do a natural sort on an array?
by ihb (Deacon) on Jun 13, 2004 at 17:30 UTC
Re: How do I do a natural sort on an array?
by Jammerwoch (Initiate) on Dec 01, 2004 at 08:11 UTC

    I wrote the following before finding the delightful Sort::Naturally library function. I recommend using that over what I've done, but maybe people are curious how it might be done. Or maybe someone needs to fine-tune or customize it.

    The following code is not efficient. In particular, the calling of naturalSortInner with $a and $b as arguments completely eliminates the efficiency of having $a and $b. However, it was necessary for the recursive nature of naturalSortInner.

    #!/usr/bin/perl sub naturalSortInner { $x = uc( shift ); $y = uc( shift ); if( !($x =~ /\d+(\.\d+)?/) ) { return $x cmp $y; } $xBefore = $`; $xMatch = $&; $xAfter = $'; if( !($y =~ /\d+(\.\d+)?/) ) { return $x cmp $y; } if( $xBefore eq $` ) { if( $xMatch == $& ) { return naturalSortInner( $xAfter, $' ); } else { return $xMatch <=> $&; } } else { return $x cmp $y; } print "\n<before: '$xBefore', match: '$xMatch', after: '$xAfter'>\ +n"; } sub naturalSort { naturalSortInner( $a, $b ); } @arr = ( 'beta', 'Alpha', 'Gamma1', 'Gamma', '23', '5', 'Version1', 'Version1.1', 'Version1.2', 'Version11.1-Sub1', 'Version11.1-Sub10', 'Version11.1-Sub3', 'x23sub5', 'Version2', 'Version2.1', 'GammaGlobulin', 'Gamma10', 'c', 'Gamma2', 'Gamma3', ); print join( "\n", sort naturalSort @arr ) . "\n";

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