6. Complex data structures - 3: Hashes of Arrays

A Hash of Arrays (1) is a Hash, where the keys are strings and the values references to anonymous arrays. You can declare a Hash Of Arrays as %HoA.

Recall to construct an anonymous array reference with square brackets: []

$anon_array_ref = ['scalar_1', 'scalar_2', 'scalar_3'];

6.1 Create

%HoA = ( # hash of arrays; notice the open and close parenthesis: it's a real hash!<
           'Sebastian' => ['red', 'blue'],
           'Daniel' => ['brown', 'green'],
           'Florence'=> ['blue', 'black', 'orange'],
      );

$HoA{'Kirsten'} = ['green','yellow'];

6.1.1 Copy

%HoA_copy = %HoA;

6.1.2 Merge

%HoA_combi = (%HoA1, %HoA2);

6.1.3 Empty

%HoA_copy = ();

6.2 Access

6.2.1 Access hash members

@color = @{$HoA{'Kirsten'}};
print("@color\n"); # output: green yellow
print("$color[1]\n"); # output: yellow

6.3 Print

%HoA_copy = %HoA;
foreach (sort(keys(%HoA_copy))) {
 print "$_ "; # output: Daniel Florence Kirsten Sebastian
}

%HoA_copy = %HoA;
foreach (sort(values(%HoA_copy))) {
 print "@$_ ";
}

%HoA_copy = %HoA;
foreach $name (sort(keys(%HoA_copy))) {
 foreach $color (sort(@{$HoA_copy{$name}})) {
  print "$name $color\n";
 }
}

Daniel brown
Daniel green
Florence black
Florence blue
Florence orange
Kirsten green
Kirsten yellow
Sebastian blue
Sebastian red

6.4 Iterate

6.5 Operate

6.5.1 Add an element

$HoA{'Bibian'} = ['red', 'green','blue'];

@mc_array = qw(green blue black);
$HoA{'Bibian'} = \@mc_array;

push(@{$HoA{'Sebastian'}},'black');

6.5.2 Remove an elementn with 'delete'

delete($HoA{'Sebastian'}) if (exists $HoA{'Sebastian'});

6.5.3 Update an element

$HoA{'Sebastian'} = ['pink', 'yellow', 'purple'];