Count elements in multidimensional arrays

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

If I create a multidimensional array using the following:

#!/usr/bin/perl
my @ar1;
$ar1[0][0] = "one";
$ar1[0][1] = "two";
$ar1[1][0] = "three";
$ar1[1][1] = "four";
$ar1[1][2] = "five";
my $count = scalar @{ $ar1[1] };
print "count = $count\n";
[download]

./ar1

count = 3

However, if I create the array this way it doesn't work:

#!/usr/bin/perl
my @ar1;
$ar1 = (["one", "two"], ["three", "four", "five"]);
my $count = scalar @{ $ar1[1] };
print "count = $count\n";
[download]

./ar1

count =

What is the correct way to access / count the array elements using the array creation method in the second code segment?

Thanks, ...Kurt

Comment on Count elements in multidimensional arrays Select or Download Code

Replies are listed 'Best First'.
Re: Count elements in multidimensional arrays by Paladin (Vicar) on May 25, 2019 at 00:00 UTC
In the second one you are assigning to `$ar1` which isn't `@ar1`. If you used `strict` and `warnings` you would have been warned about this.	[reply] [d/l] [select]
Re: Count elements in multidimensional arrays by BillKSmith (Monsignor) on May 25, 2019 at 12:23 UTC
Paladin has already shown that you could have found your error yourself if you had used the pragmas "strict" and "warnings". Also note that a little extra whitespace to align your array definition can make it easier to read. That alone can help to avoid errors in accessing them. `use strict; use warnings; my @ar1 = ( ["one", "two", ], ["three", "four", "five", ], ); my $count = scalar @{ $ar1[1] }; print "count = $count\n";` [download] Bill	[reply] [d/l]
Re: Count elements in multidimensional arrays by Marshall (Canon) on May 26, 2019 at 01:40 UTC
In Perl, a 2-D array is an array of references to 1-D arrays. Look at Data Type: Array in the Tutorials section of Perl Monks. A Perl 2-D array can have a different number of "columns" on each "row". `#!/usr/bin/perl use strict; use warnings; my @ar1 = (["one", "two"], ["three", "four", "five"]); my $count = scalar @{ $ar1[1] }; print "count: Elements in 2nd Row = $count\n"; print "number of dimensions =", scalar @ar1, "\n"; my $total_elements; foreach my $row_ref (@ar1) { $total_elements += @$row_ref; } print "total elements in array:ar1=$total_elements\n"; __END__ count: Elements in 2nd Row = 3 number of dimensions =2 total elements in array:ar1=5` [download]	[reply] [d/l]


Perl: the Markov chain saw
	PerlMonks