删除 Perl 中的数组数组中的 undef

Question

I am trying to remove the element from the array of array which has undef value.

I want the output to be:

@list = [
      [
        2,
        ""
      ],
      [
        4,
        ""
      ],
      [
        6,
        ""
      ],
      [
        8,
        ""
      ],
      [
        10,
        ""
      ],
    ];

This is what I have been trying to remove the undef from the array. I am grepping the defined element from the array, but its not working

use Data::Dumper;

my @list = [
  [
    undef,
    ""
  ],
  [
    2,
    ""
  ],
  [
    4,
    ""
  ],
  [
    6,
    ""
  ],
  [
    8,
    ""
  ],
  [
    10,
    ""
  ],
];

@list = grep defined, @list;

print Dumper(\@list);

Can someone please help?

Thanks in advance

Answer 1

People often get lists and arrays confused in Perl. So calling an array variable @list is a really bad idea:-)

As I mentioned in a comment, you seem to be confused about how you populate an array in Perl. You either populate it with a list:

my @array = ( ... ); # Lists use parentheses

Or you create an anonymous array and store a reference to that array in a scalar variable:

my $array_ref = [ ... ]; # Anon array uses square brackets

Next, your array doesn't contain undef elements. Every element in your array is a reference to a two-element array. In one of those second-level arrays, the first element is undef . You're right to use grep to filter the array, but you need to look at the second-level array to do what you want.

So the code would look something like this:

my @array = ( ... );

@array = grep { defined $_->[0] } @array;

Note that I've switched to the block syntax of grep . This is the most commonly-used version and it's probably best to use that syntax.