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Re^3: [ Natural Sort ]: Sorting a string with numbers

by blueflashlight (Pilgrim)
on Sep 18, 2005 at 02:01 UTC ( #492963=note: print w/replies, xml ) Need Help??


in reply to Re^2: [ Natural Sort ]: Sorting a string with numbers
in thread [ Natural Sort ]: Sorting a string with numbers

The whole program is a bit complex and does a bunch of stuff that isn't relavent to this issue, but I've cut out everything but this section that shows the problem I'm having.
#!/usr/bin/perl -w use strict; my @h = ( qw( psapp1 psapp psapp2 psepapp1 psepapp psepapp2 psimgprod pspappuat pswebapp2 pswebapp ) ); my @h_sorted = @h[ map { unpack "N", substr($_,-4) } sort map { my $key = $h[$_]; $key =~ s[(\d+)][ pack "N", $1 ]ge; $key . pack "N", $_ } 0..$#h ]; foreach (@h_sorted) { print "$_\n"; };

When I run this program, with my Perl (This is perl, v5.8.6 built for darwin-thread-multi-2level), I get:
psapp psapp1 psapp2 psepapp1 psepapp2 psepapp psimgprod pspappuat pswebapp2 pswebapp
The "psapp" items sort properly, but the "psepapp" and "pswebapp" ones show the problem I'm asking about. Thanks! -s-

Replies are listed 'Best First'.
Re^4: [ Natural Sort ]: Sorting a string with numbers (fix)
by tye (Sage) on Sep 18, 2005 at 03:25 UTC

    Yeah, that's the problem I discussed elsewhere. Here's a simple fix:

    #!/usr/bin/perl -w use strict; my @h = ( qw( psapp1 psapp psapp2 psepapp1 psepapp psepapp2 psimgprod pspappuat pswebapp2 pswebapp ) ); my @h_sorted = @h[ map { unpack "N", substr($_,-4) } sort map { my $key = $h[$_]; $key =~ s[(\d+)][ pack "N", $1 ]ge; $key . pack "CNN", 0, 0, $_ } 0..$#h ]; foreach (@h_sorted) { print "$_\n"; };

    This inserts 5 nul bytes which prevents the problem. 1 nul byte is enough to fix this specific case. 4 fixes all cases except for the possibility of "x0" sorting before "x". 5 fixes all cases (provided you don't have nul bytes in your strings).

    - tye        

      You are a hero. Thank you so much ... I even understand your solution, which, in itself is amazing. :-)

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