Re: two order sort

Multi-key sort, both in descending order:

>perl -wMstrict -le
"use List::Util qw(sum);
 ;;
 my $scan = {
   a => [ 5, 6 ], b => [ 5, 10, 15 ], c => [ 100 ], d => [ 8, 9 ]
   };
 ;;
 my @sorted =
   map  $_->[0],
   sort { $b->[1] <=> $a->[1]  or  $b->[2] <=> $a->[2] }
   map  [ $_,  scalar @{ $scan->{$_} },  sum @{ $scan->{$_} } ],
   keys %$scan
   ;
 ;;
 print qq{@sorted};
"
b d a c
[download]

Comment on Re: two order sort Download Code

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Re^2: two order sort by LanX (Saint) on Mar 05, 2013 at 01:30 UTC
you forgot to tell that your (Schwarzian) approach is not only better readable but much faster, because the sums are only calculated once per entry. =) Cheers Rolf	[reply]
Re^3: two order sort by AnomalousMonk (Archbishop) on Mar 05, 2013 at 02:25 UTC
A ~~decorate-sort-undecorate or~~ GRT (Guttman-Rosler Transform) approach would be even faster, but I forgot how to decorate for descending sort. It's probably somewhere in A Fresh Look at Efficient Perl Sorting. Must look it up... Updates: See also Sort::Maker. According to the Wikipedia article linked by LanX herein, "decorate-sort-undecorate" is just another term for "Schwartzian Transform".	[reply]
Re^4: two order sort by BrowserUk (Patriarch) on Mar 05, 2013 at 03:49 UTC
I forgot how to decorate for descending sort. Just negate the field(s). Unary minus ('-') for numeric and boolean not ('~') for alpha: # Ascending numeric and ascending alpha print for map{ unpack 'x[Na4]a', $_ } sort map{ local $^W; pack 'Na4a', (0+$_), substr( $_, 1), $_ } @a;; 0cjlf 0dvys 0uvmu 1akkn 1imwi 1lpys 1pjzw 2uwep 3hiyn 3jrkx 3myrn 3ozcw 3rqhx 3vkon 6excm 7axqf 7lbhj 8klfd 9ijei 9klou # Descending numeric and ascending alpha print for map{ unpack 'x[Na4]a', $_ } sort map{ local $^W; pack 'Na4a', -(0+$_), substr( $_, 1), $_ } @a;; 0cjlf 0dvys 0uvmu 9ijei 9klou 8klfd 7axqf 7lbhj 6excm 3hiyn 3jrkx 3myrn 3ozcw 3rqhx 3vkon 2uwep 1akkn 1imwi 1lpys 1pjzw # Ascending numeric and descending alpha print for map{ unpack 'x[Na4]a', $_ } sort map{ local $^W; pack 'Na4a', (0+$_), ~substr( $_, 1), $_ } @a;; 0uvmu 0dvys 0cjlf 1pjzw 1lpys 1imwi 1akkn 2uwep 3vkon 3rqhx 3ozcw 3myrn 3jrkx 3hiyn 6excm 7lbhj 7axqf 8klfd 9klou 9ijei # Decending numeric and descending alpha print for map{ unpack 'x[Na4]a', $_ } sort map{ local $^W; pack 'Na4a', -(0+$_), ~substr( $_, 1), $_ } @a;; 0uvmu 0dvys 0cjlf 9klou 9ijei 8klfd 7lbhj 7axqf 6excm 3vkon 3rqhx 3ozcw 3myrn 3jrkx 3hiyn 2uwep 1pjzw 1lpys 1imwi 1akkn [download] With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday' Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice.	[reply] [d/l]
Re^5: two order sort by AnomalousMonk (Archbishop) on Mar 05, 2013 at 07:04 UTC
Re^6: two order sort by BrowserUk (Patriarch) on Mar 05, 2013 at 15:11 UTC
Re^4: two order sort by LanX (Saint) on Mar 05, 2013 at 09:41 UTC
> > your (Schwarzian) approach is not only better readable ... > A decorate-sort-undecorate or GRT approach would be even faster, I'm confused, IMHO "Schwartzian Transform" and "Decorate-Sort-Undecorate" are two names of the same thing ... right ??? EDIT: see also Decorate-Sort-Undecorate in WP. UPDATE: OK I got it. You were referring to GRT beeing faster. =) (Advanced Sorting - GRT - Guttman Rosler Transform) Well in this case creating a float separating the two numeric values by a point should be fast enough. Cheers Rolf	[reply]
Re^5: two order sort by AnomalousMonk (Archbishop) on Mar 05, 2013 at 22:01 UTC
Re^4: two order sort by ag4ve (Monk) on Mar 07, 2013 at 16:11 UTC
Thanks for the routine and the module (and the article - I'll have to read that). The code works great.	[reply]

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