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Getting confused with 2d arrays

Posted on 2008-06-11
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Last Modified: 2011-09-20
Hi,

I just built a 2D array, and I want to iterate over all elements for printing. I tried this:

for ($i = 0; $i < @rows; $i++) {
    for ($j = 0; $j < @rows[$i]; $j++) {
        print($rows[$i][$j], "  ");  
    }
    print("\n");
}

where @rows is my 2D array, but the script just executes in an infinite loop. I'm guessing the problem is:

      $j < @rows[$i]

in that statement I mean to say the length of the 1d array in element $i of the 2D array. What's the right syntax for it?

thanks
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Question by:DJ_AM_Juicebox
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6 Comments
 
LVL 39

Expert Comment

by:Adam314
ID: 21761331

for(my $i = 0; $i < @rows; $i++) {
	for (my $j = 0; $j < @{$rows[$i]}; $j++) {
		print($rows[$i][$j], "  ");  
	}
	print("\n");
}

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LVL 13

Expert Comment

by:marchent
ID: 21761414
Here you'll find how to iterate the 2d array with example http://icfun.blogspot.com/2008/03/perl-two-dimensional-array-handling.html
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Author Comment

by:DJ_AM_Juicebox
ID: 21762045
Ehh still seems to just loop endlessly. Here's my entire script:




my @rows = ( [2, 4, 6],
             [3, 6, 9],
           );

for (my $i = 0; $i < @rows; $i++) {
    for (my $j = 0; $j < @{rows[$i]}; $j++) {
        print($rows[$i][$j], "  ");  
    }
}
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LVL 39

Accepted Solution

by:
Adam314 earned 500 total points
ID: 21762470
You are missing the $ in front of rows[$i].  It should be:
The @{$rows[$i]} means:
    take $rows[$i], which is a reference to an array
    Then take that array

Then the $j < mean interpret that array in scalar context, which means return the number of elements in the array.
my @rows = ( [2, 4, 6],
             [3, 6, 9],
           );
 
for (my $i = 0; $i < @rows; $i++) {
    for (my $j = 0; $j < @{$rows[$i]}; $j++) {
        print($rows[$i][$j], "  ");  
    }
}

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Author Comment

by:DJ_AM_Juicebox
ID: 21763025
ok you're right, thanks.
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LVL 84

Expert Comment

by:ozo
ID: 21763984
It may be safer to itterate
for my $i( $[ .. $#rows ){ for my $j ( $[ .. $#{$rows[$i]} )
Or a simpler way is
print "@$_\n" for @rows;
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