Showing entries with tag "Array".

Found 8 entries

Perl: Find unique items in an array

I need to extract all the unique elements from an array. There is no built-in way to do this, but there are several user functions you can use.

my @x = qw(one two one three one four);
my @y = array_unique(@x); # ("one", "two", "three", "four")
# Borrowed from: https://perlmaven.com/unique-values-in-an-array-in-perl
sub array_unique {
    my %seen;
    return grep { !$seen{$_}++ } @_;
}

I stand corrected, List::Util includes a uniq() function to do exactly this, is a core module, and is included with all Perl installations.

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Perl: Extract a column from a hashref

I have an array full of hash references and I need to extract a column and build an array from that.

my @x = ( {'ip' => '127.0.0.1'}, {'ip' => '10.10.10.10'}, {'ip' => '192.168.5.6'} );
my @y = hash_column('ip', @x); # ["127.0.0.1", "10.10.10.10", "192.168.5.6"]
sub hash_column {
    my $col = shift();
    my @arr = @_;

    my @ret;
    foreach my $x (@arr) {
        push(@ret, $x->{$col});
    }

    return @ret;
}
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Perl: Find the longest string in an array

I need a Perl way to find the maximum string length in an array so here is a function to do that:

my @words = qw(Apple Pear Watermelon Banana Cherry);
my $max   = max_length(@words); # 10
sub max_length {
    my $max = 0;

    foreach my $item (@_) {
        my $len = length($item);
        if ($len > $max) {
            $max = $len;
        }
    }

    return $max;
}
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Perl: array_chunk() to split arrays into smaller chunks

I have an large array in Perl that I need in smaller chunks to make iteration easier. I borrowed a concept from PHP and implemented array_chunk() in Perl.

my @orig = qw(foo bar baz one two three red yellow green donk);
my @new  = array_chunk(3, @orig);
sub array_chunk {
    my ($num, @arr) = @_;
    my @ret;

    while (@arr) {
        push(@ret, [splice @arr, 0, $num]);
    }

    return @ret;
}
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Perl: find the index of an array item

I needed to find the index of an item in an array so I wrote a simple Perl function.

my @arr = qw(foo bar baz donk);
my $x   = array_index("bar", @arr)); # 1
sub array_index {
    my ($needle, @haystack) = @_;

    if (defined($needle)) {
        for (my $idx = 0; $idx < @haystack; $idx++) {
            if ($haystack[$idx] eq $needle) {
                return $idx;
            }
        }
    }

    return undef;
}
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Perl: doing a regexp replace on an array

I have an array of items that I want to do a quick regexp replace on each element. Here is a very elegant solution:

@names = ("John", "Paul", "george", "Ringo");
s/^g/G/g for @names;
print join(", ",@names);
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Remove an item from a PHP array

Given an array in PHP, I need to remove a specific element (if it exists in the array) from the array. The following is a pretty simple and elegant solution. I didn't use unset on purpose because you have to check for a integer result before you remove the item from the array.

$arr     = array('apple','banana','orange');
$new_arr = array_diff($arr, array('banana'));

print_r($new_arr);
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Perlfunc: in_array()

If you need to determine if an array contains a specific element you can use this function:

sub in_array {
    my ($needle, @haystack) = @_;

    foreach my $l (@haystack) {
        if ($l eq $needle) { return 1; }
    }

    return 0;
}

Note: If you want to check integers just change the eq to ==

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