Question

Consider the binary tree developed in Moose::Cookbook::Basics::Recipe3

To retrieve all nodes in preorder, I could add the following subroutine to the BinaryTree package

sub pre_order {
  my ($self,$aref) = @_;

  push @$aref, $self->node;

  pre_order($self->left,$aref) if $self->has_left;
  pre_order($self->right,$aref) if $self->has_right;
}

The sub would have to be used like this:

my $btree = BinaryTree->new;
#add some nodes

#then later...
my @nodes_in_preorder;
$btree->pre_order(\@nodes_in_preorder);

How would i have to change the subroutine to be able to use syntax like the below:

my @nodes_in_preorder = $btree->pre_order();

in order to be able to do things like

for ($btree->pre_order()) { #bla bla } 

later on.

Does this make sense, or am I being to pedantic?

Answer 1

How about:

sub pre_order {
  my $self = shift;
  return ($self->node,
    $self->has_left ? $self->left->pre_order : (),
    $self->has_right ? $self->right->pre_order : ());
}