在Perl中打印二维数组的第一行

Question

I have the below code and I'm attempting to print out only the first row of this 2d array

# how many columns
for (my $c = 0; $c <= $#list[0]; $c++) {
print $list[0][$c]."\n";

the data should be something like

[0] => "ID,Cluster,Version"
[1] => "2,32,v44"

The Error:

syntax error at ./connect_qb.pl line 107, near "$#list["
syntax error at ./connect_qb.pl line 107, near "++) "
Execution of ./connect_qb.pl aborted due to compilation errors.

Answer 1

$list[0]

is a reference to an array, so the array is

@{ $list[0] }

so the last element of that array is

$#{ $list[0] }

so you'd use

for my $c (0 .. $#{ $list[0] }) {
   print "$list[0][$c]\n";
}

or

for (@{ $list[0] }) {
   print "$_\n";
}

Answer 2

You should avoid c-style for loops. Here's one way to do it.

use strict;
use warnings;
use feature qw(say);

my @a = (["ID","Cluster","Version"], ["2","32","v44"]);
say for (@{$a[0]});

A slightly less confusing dereferencing:

...
my $ref = $a[0];
say for (@$ref);

Answer 3

这是一个简单的班轮

print join(",",@{$list[0]}),"\n";

Answer 4

Try this:

for (my $c = 0; $c <=  (scalar @{$list[0]}); $c++) 

for the loop condition