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Re: sorting keys in hash

by farang (Hermit)
on May 23, 2014 at 23:08 UTC ( #1087276=note: print w/ replies, xml ) Need Help??


in reply to sorting keys in hash

Yet another way, though I totally agree that a much better solution would be to use an inherently sortable format for the hash keys from the start.

use strict; use warnings; use feature 'say'; my %data = ( Apr14 => 2, Mar14 => 2, May14 => 2, Dec13 => 2, ); my %month_to_num = ( Jan => '01', May => '05', Sep => '09', Feb => '02', Jun => '06', Oct => '10', Mar => '03', Jul => '07', Nov => '11', Apr => '04', Aug => '08', Dec => '12', ); my %num_to_month = reverse %month_to_num; say "key - $_ and value - $data{$_}" for map { s/ (\d{2}) (\d{2}) /$num_to_month{$2}$1/rx } sort map { s/ (\w{3}) (\d{2}) /$2$month_to_num{$1}/rx } keys %data;


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Re^2: sorting keys in hash
by AnomalousMonk (Abbot) on May 24, 2014 at 01:16 UTC

    If you're going to go to the trouble of two  s/// operations, you might as well go all the way to a GRT/decorate-sort-undecorate solution; then you can at least claim to be getting the maximum possible performance from the Perl sort built-in.

    c:\@Work\Perl\monks>perl -wMstrict -le "my %data = qw( Dec02 2 Jan02 3 May05 4 Dec14 8 Dec01 5 Jan14 7 Apr05 6 Feb14 9 May15 10 ); ;; use constant Y_WID => 2; use constant M_WID => 3; my %mon_n = qw( Jan 1 Feb 2 Mar 3 Apr 4 May 5 Jun 6 Jul 7 Aug 8 Sep 9 Oct 10 Nov 11 Dec 12 ); ;; my @sorted_dates = map unpack(qq{x${\Y_WID} x${\M_WID} a*}, $_), sort map sprintf('%*s%*s%s', Y_WID, $_->[1], M_WID, $mon_n{$_->[0]}, $_- +>[2]), map [ m{ \A ([[:alpha:]]{${\M_WID}}) (\d{${\Y_WID}}) \z }xms, $_ ], keys %data ; ;; print qq{Key - $_ and b value - $data{$_}} for @sorted_dates; " Key - Dec01 and b value - 5 Key - Jan02 and b value - 3 Key - Dec02 and b value - 2 Key - Apr05 and b value - 6 Key - May05 and b value - 4 Key - Jan14 and b value - 7 Key - Feb14 and b value - 9 Key - Dec14 and b value - 8 Key - May15 and b value - 10

    Update: See A Fresh Look at Efficient Perl Sorting by Guttman and Rosler (the G and R of GRT). Also: It seems to me now that all the regex sub-string extraction and sprintf-ing would have been much neater, clearer and more maintainable if encapsulated into a separate function. Oh, well...

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