Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

Ok, this is probably a silly question, but from the following code how do I reference a row and column value, and change the value, and or print a value: 
    my @matrix = 
    (
    [qw( . . . 1 0 0 1 0 1 0 1)],
    [qw( . . 0 1 2 3 4 5 6 7 8)],
    [qw( . 0 . . . . . . . . .)],
    [qw( 0 1 . . . . . . . . .)],
    [qw( 1 2 . . . . . . . . .)],
    [qw( 0 3 . . . . . . . . .)],
    [qw( 1 4 . . . . . . . . .)],
    [qw( 1 5 . . . . . . . . .)],
    [qw( 0 6 . . . . . . . . .)],
    [qw( 1 7 . . . . . . . . .)],
    [qw( 1 8 . . . . . . . . .)],
    [qw( 0 9 . . . . . . . . .)],
    [qw( 1 7 . . . . . . . . .)],
    );

    foreach $row (@matrix) {
        print "@$row\n";
    }

[download]
thanks for the help

Replies are listed 'Best First'.
Re: Array of Array Row Reference
by strat (Canon) on Mar 04, 2002 at 14:51 UTC
    Well, you've got a two-dimensional array, which in perl is a list () of references to lists [].
    If you want to get the element 0/4, just write: 
    my $element = $matrix[0]->[4]; 
# or by shorthand:
my $element2 = $matrix[0][4];

    [download]
    If you want to change the element 6/3 to 8, just write 
    $matrix[6]->[3] = 8; # or the same shorthand as above

    [download]
    If you want go get the whole row number 6: 
    my @row6 = @{ $matrix[6] }; # to a list
my $listRef6 = $matrix[6]; # to a listreference

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    If you want to print this array formatted, you could also do the following: 
    foreach my $row (@matrix) {
  print join ("\t", @$row);
}

    [download]
    Further information gives you: perldoc perllol

    Best regards,
    perl -le "s==*F=e=>y~\*martinF~stronat~=>s~[^\w]~~g=>chop,print"

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(jeffa) Re: Array of Array Row Reference
by jeffa (Bishop) on Mar 04, 2002 at 14:44 UTC
    Using the code you have, this snippet will print the fourth column from the second row: 
    print $matrix[1]->[3], "\n";

    [download]

    jeffa

    L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)
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[d/l]

      Using the code you have, this snippet will print the fourth column from the second row: print $matrix[1]->[3], "\n";

      Which can also be written as print $matrix[1][3], which is more multi-dimensional-array-like. 

      ++ vs lbh qrpbqrq guvf hfvat n ge va Crey :)
Nabgure bar vs lbh qvq fb jvgubhg ernqvat n znahny svefg.
-- vs lbh hfrq OFQ pnrfne ;)
    - Whreq

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Re: Array of Array Row Reference
by joealba (Hermit) on Mar 04, 2002 at 14:41 UTC
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