http://qs321.pair.com?node_id=559809

0xbeef has asked for the wisdom of the Perl Monks concerning the following question:

I am struggling to find a solution in sorting a reasonably complex hash-of-hashes directly if the sort key is located a number of levels below the first keys in the hash.

I bypass this problem (inefficiently) by deriving a second simplified hash through which I can then sort by time.

Hopefully this simplified example will illustrate it more clearly:

#!/usr/bin/perl -w use strict; my %ERROR; my %ERROR2; my @classes = ('H','S','O'); my $output = <<EOD; 4865FA9B 0702 P H rmt0 TAPE OPERATION ERROR DE9A52D1 0704 I S rmt0 DEVICE DUMP RETRIEVED 4865FA9B 0701 P H rmt2 TAPE OPERATION ERROR F3E9B3E2 0620 I O SYSJ2 UNABLE TO ALLOCATE SPACE IN FILE SY +STEM DCB47997 0511 T H hdisk4 DISK OPERATION ERROR EOD # populate original hash for my $line (split /\n/,$output) { chomp $line; my ($IDENTIFIER,$TIMESTAMP,$T,$C,$RES,$DESC) = split(/\s+/,$line,6) +; $ERROR{$C}{$RES}{$DESC}{time} = $TIMESTAMP; $ERROR{$C}{$RES}{$DESC}{id} = $IDENTIFIER; $ERROR{$C}{$RES}{$DESC}{T} = $T; } # elsewhere, I create a secondary hash for sorting. my $counter = 0; for my $CLASS (@classes) { for my $RES (keys %{$ERROR{$CLASS}}) { for my $DESC (keys %{$ERROR{$CLASS}{$RES}}) { $counter++; $ERROR2{$CLASS}{$counter}{time} = $ERROR{$CLASS}{$RES}{$DESC} +{time}; $ERROR2{$CLASS}{$counter}{desc} = $DESC; # ... transfer some other data from %ERROR to %ERROR2 } } } # ... # output - SORT EACH CLASS BY MOST RECENT TIME. # sort using CLASS as primary and time as secondary key. # note how RES and DESC have no influence on the sorting. for my $CLASS (@classes) { for my $nr (reverse sort {$ERROR2{$CLASS}{$a}{time} <=> $ERROR2{$CLA +SS}{$b}{time} } keys %{$ERROR2{$CLASS}}) { print "CLASS $CLASS : Time : $ERROR2{$CLASS}{$nr}{time} Descript +ion: $ERROR2{$CLASS}{$nr}{desc}\n"; } }

I know a possibility would be to reconstruct the original hash in the %ERROR2 format - but this is not feasible due to other issues, so I'm stuck with two hashes to avoid the effect that RES and DESC keys would have when traversing %ERROR in a for loop.

Is there a method which would avoid the need for %ERROR2, and still provide output of "each class sorted by time"?

-Niel