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2D array length (again!)

LerdoPerlo
New User

Feb 22, 2010, 9:13 AM

Post #1 of 4 (333 views)

2D array length (again!)	Can't Post

Hi,

I'm sure this has been asked several times before, but I can't seem to find a proper answer.

Say I have the following two-dimensional array:

Code

@A = ( [00, 01, 02, 03], 
       [10, 11, 12, 13, 14, 15, 15, 17, 18], 
       [20, 21, 22, 23, 24, 25, 26, 27], 
       [30, 31], 
       [40], 
       [50, 51, 52] 
     );

I've found that if I print the size of @A using:

Code

print "size of A: " . @A . "\n";

I get the expected value: 6

But if I try to find the size of each of the arrays within @A and I go further than its real size, that is:

Code

print "size of A[0]: " . $#{$A[0]} . "\n"; 
print "size of A[1]: " . $#{$A[1]} . "\n"; 
print "size of A[2]: " . $#{$A[2]} . "\n"; 
print "size of A[3]: " . $#{$A[3]} . "\n"; 
print "size of A[4]: " . $#{$A[4]} . "\n"; 
print "size of A[5]: " . $#{$A[5]} . "\n"; 
print "size of A[6]: " . $#{$A[6]} . "\n"; 
print "size of A[7]: " . $#{$A[7]} . "\n"; 
print "size of A[8]: " . $#{$A[8]} . "\n";

The next time I print the size of @A, it says it's now 9 elements big.

Furthermore: How one would add a new column in the last row (ie, an element to the last array of @A)? I was expecting this to work, but didn't:

Code

$A[ @A -1 ][ $#{$A[ @A -1 ]} ] = "new element";

toolic
User

Feb 22, 2010, 10:05 AM

Post #2 of 4 (327 views)

Re: [LerdoPerlo] 2D array length (again!) [In reply to]	Can't Post

Each of the last 3 prints (6-8) increased the array size because of autovivification.

One way to add an element is to index the last row using -1, then do a push:

Code

push @{ $A[-1] }, "new element";

shawnhcorey
Enthusiast

Feb 22, 2010, 1:35 PM

Post #3 of 4 (322 views)

Re: [LerdoPerlo] 2D array length (again!) [In reply to]	Can't Post

You should use a loop to access the contents of @A:

Code

#!/usr/bin/perl 
 
use strict; 
use warnings; 
 
my @A = ( [00, 01, 02, 03],  
  [10, 11, 12, 13, 14, 15, 15, 17, 18],  
  [20, 21, 22, 23, 24, 25, 26, 27],  
  [30, 31],  
  [40],  
  [50, 51, 52]  
); 
 
print "The size of \@A is ", scalar( @A ), ".\n"; 
for my $i ( 0 .. $#A ){ 
  print "The size of \@{\$A[$i]} is ", scalar( @{$A[$i]} ), ".\n"; 
}

__END__

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LerdoPerlo
New User

Feb 23, 2010, 5:10 AM

Post #4 of 4 (312 views)

Re: [shawnhcorey] 2D array length (again!) [In reply to]	Can't Post

Thank you very much, guys! With your information I've achieved what I needed. THANKS! Wink

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