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Re: Array vs. Hash for sparsely integer-indexed data

by blue_cowdawg (Monsignor)
on Jan 25, 2013 at 19:36 UTC ( #1015395=note: print w/replies, xml ) Need Help??


in reply to Array vs. Hash for sparsely integer-indexed data

      My perl program frequently needs to retrieve a cached set of data that is indexed by a positive but sparsely populated set of integers.

By the way it's Perl. Lower case perl is the command. Oh... never mind.

Based on what you said I'd go with a hash. If you really want to implement a sparse array you could to this:

package IndexedSparseArry; sub new { shift; my $self={ array => [ ] }; bless $self,"IndexedSparseArray"; } sub insert { my ($self,$index,$data)=@_; my @work = @{$self->{array}}; if ( $#work == -1 ) { # Nothing there yet. push @work,{index => $index, data => $data}; } else { my $i=0; # not to be confused with index. while ( ($i < $#work) && ($work[$i]->{index} < $index)){ $i++ } if ( $i == $#work ) { if ($work[$1] < $index ) { push @work,{index => index, data => $data); } else { $work[$i+1]=$work[$i]; $work[$i] = { index => $index, data=>$data}; } } else { my $j = $#work + 1; while ($j > $i){ $work[$j] = $work[$j-1]; $j--; } $work[$i] = { index => $index, data => $data }; $self->{array} = [@work]; } 1;
Save that file to IndexedSparseArray.pm and in your main program:
use strict; use warnings; use IndexedSparseArray; my $repo = IndexedSparseArray->new(); while (<i am reading in data >){ | handwaving $repo->insert($index,$data); } | etc.
Big Caveat: I didn't test this and I was interrupted a bunch of times. This should work, but...

I think I've given you something to chew on, hope it helps.


Peter L. Berghold -- Unix Professional
Peter -at- Berghold -dot- Net; AOL IM redcowdawg Yahoo IM: blue_cowdawg

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[MidLifeXis]: I think I forgot "running on a farm of commodore 64, vic 20s, trs 80s, and apple ]|[e systems"
[GotToBTru]: oh I know what it is .. but it is a number only slightly useful to me and of no possible use to our customer
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