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Matrix Declaration / Data Structure Syntax Question

by oxirane (Initiate)
on Mar 09, 2013 at 15:39 UTC ( #1022583=perlquestion: print w/replies, xml ) Need Help??
oxirane has asked for the wisdom of the Perl Monks concerning the following question:

I was exploring some of the dynamic alignment programs for protein and DNA used by biologists and came across a data construct that I didn't understand...could someone explain the square bracket/square bracket/curly bracket reference construct and comment on it being a good/bad way to go about dynamic matrix declaration

@matrix; $matrix[0][0]{score} = 0; $matrix[0][0]{pointer} = "none"; for($j = 1; $j <= length($seq1); $j++) { $matrix[0][$j]{score} = 0; $matrix[0][$j]{pointer} = "none"; } for ($i = 1; $i <= length($seq2); $i++) { $matrix[$i][0]{score} = 0; $matrix[$i][0]{pointer} = "none";

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Re: Matrix Declaration / Data Structure Syntax Question
by kcott (Chancellor) on Mar 10, 2013 at 00:49 UTC

    G'day oxirane,

    Welcome to the monastery.

    When presented with a complex data structure, you may find Data::Dumper to be a useful tool.

    Here's a simplified version of your matrix:

    $ perl -Mstrict -Mwarnings -e ' use Data::Dumper; my @matrix; for my $i (0 .. 1) { for my $j (0 .. 1) { $matrix[$i][$j]{row} = $i; $matrix[$i][$j]{col} = $j; } } print Dumper \@matrix; ' $VAR1 = [ [ { 'col' => 0, 'row' => 0 }, { 'col' => 1, 'row' => 0 } ], [ { 'col' => 0, 'row' => 1 }, { 'col' => 1, 'row' => 1 } ] ];

    -- Ken

Re: Matrix Declaration / Data Structure Syntax Question
by bioinformatics (Friar) on Mar 09, 2013 at 17:32 UTC
    It's an array of arrays (two dimensional array) with matrix[i][j] pointing to a hash with defined keys (score and pointer). Arrays of arrays (denoted AoA) and hashes of hashes (HoH) are pretty useful and I use them constantly. I'd say it was a good way to keep everything in one data structure while maintaining speed and readability of the code.

Re: Matrix Declaration / Data Structure Syntax Question
by AnomalousMonk (Chancellor) on Mar 09, 2013 at 18:51 UTC
Re: Matrix Declaration / Data Structure Syntax Question
by CountZero (Bishop) on Mar 10, 2013 at 12:11 UTC
    It is neither good nor bad. It is simply the way Perl uses multi-dimensional variables.


    A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James

    My blog: Imperial Deltronics
Re: Matrix Declaration / Data Structure Syntax Question
by Anonymous Monk on Mar 09, 2013 at 15:54 UTC

    Do you know the types of variables in perl? In other words, have you read perlintro/perldata/ Modern Perl ch 3?

    { 'hashes', 'are', 'curly', 'ones' }

    [ 'arrays', 'are', 'square' ]

    ( 'lists are round' )

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[Corion]: Eily: Sure, that's what I do, but some things you need to do on the Android device directly, like when navigating the bootloader :-)
[Eily]: marto you just need a longer cable :P
[Corion]: marto: Yeah, but I'm somewhat wary of installing random USB drivers downloaded from , Google Drive or whatever, so Linux wins there due to there being no conflicts and me just having to edit one text file in the worst case, to add the USB vendor
[hippo]: Long USB cable FTW.
[Corion]: Eily: I've thought of that, but I don't like running long cables through the appartment because sooner or later I'll trip over it, pulling at least one device off its stand :)
[marto]: hmm, may have to patch CPAN::Meta to move from search.cpan to metacpan in the META.json/yml files
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[Corion]: And I think it's better to generate links to the new world instead of keeping the older links alive by generating new versions of them ;)
[marto]: yeah, I guess it's supposed to be a permanent redirect, but better to make the move where possible

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