# Visitor Pattern in Perl, using package/bless appraoch to oop

# we're going to implement visitees as linked list cells

package visitee;

sub newvisitee
{
   my $t = $_[0];
   my $hash = 
    {  "tail" => $t
    };
   bless $hash, visitee;
}

sub accept
{
  my ($this,$visitor1) = @_;
  visitor->visit($visitor1,$this);
}



package singleton;   @ISA = ("visitee");

sub newsingle
{
   my ($x,$t) = @_;
   my $hash = visitee->newvisitee($t);
   $hash->{"head"} = $x;
   bless $hash, "singleton";
}

package couple;   @ISA = ("visitee");

sub newcouple
{
   my ($x,$y,$t) = @_;
   my $hash = visitee->newvisitee($t);
   $hash->{"left"} = $x;
   $hash->{"right"} = $y;
   bless $hash, "couple";
}

package