# {{{ tstruct                      have 2 trees same structure? (must be normalized)
#
sub tstruct {
  my $t1   = shift;                  # get reference to "root" of tree1
  my $t2   = shift;                  # get reference to "root" of tree2
  my $safe = shift || FALSE;         # Flag for safe comparison (normalize first)

  if($safe == TRUE) {                # If safe comparison should happen
    &tnormalize($t1);                # Normalize Tree1
    &tnormalize($t2);                # Normalize Tree2
  }

  # Exit if one of them is leaf and the other isn't
  return FALSE if(( $t1->is_leaf($t1) && !$t2->is_leaf($t2)) or
		  (!$t1->is_leaf($t1) &&  $t2->is_leaf($t2)));
  # exit if they have different amount of children
  return FALSE if($t1->n_children($t1) != $t2->n_children($t2));

  return TRUE  if($t1->is_leaf($t1));   # if t1 is leaf -> both are: OK

  # => HERE BOTH ARE PARENTS WITH SAME AMOUNT OF CHILDREN

  # get the children references for $t1 and $t2
  my @t1childs;
  my @t2childs;
  $t1->children_foreach($t1,$Tree::Nary::TRAVERSE_ALL,\&_pchild_ref,\@t1childs);
  $t2->children_foreach($t2,$Tree::Nary::TRAVERSE_ALL,\&_pchild_ref,\@t2childs);
  # get the amount of grandchildren ordered
  my %grand1;
  my %grand2;
  for my $i (0 ... scalar(@t1childs)-1) {     # iterate all children by index
    my $ngk1 = $t1childs[$i]->n_children($t1childs[$i]);   # amount of grandkids1
    my $ngk2 = $t2childs[$i]->n_children($t2childs[$i]);   # amount of grandkids2
    $grand1{$ngk1} = () if(!exist($grand1{$ngk1}));
    push $grand1{$ngk1}, $t1childs[$i];
    $grand2{$ngk2} = () if(!exist($grand2{$ngk2}));
    push $grand2{$ngk2}, $t2childs[$i++];
  }
  # NOW WE HAVE IN THE grand1 & grand2 HASHES THE DISTRIBUTION OF THE GRANDCHILDREN
  # OF THE CHILDREN PLUS THE CORRESPONDENDING CHILDREN REFERENCES

  # ensure, that the distributions have same amount of entries
  return FALSE if(scalar(keys %grand1) != scalar(keys %grand2));

  while (my ($key, $value) = each %grand1) {  # iterate all T1 grandchild distributions
    # exit if distribution varies, because they must have same length also,
    # the following condition ensures we have same distribution in grand1 and grand2
    return FALSE if(scalar($grand1{$key}) != scalar($grand2{$key}));
  }
  # NO WE HAVE TWO IDENTICAL DISTRIBUTIONS AT CHILD/GRANDCHILD LEVEL
  while (my ($key, $value) = each %grand1) {  # iterate all T1 grandchild distributions
    if($key > 0) {   # we don't need to consider children that are leafs
      
      # ULTRABRUTAL CORE RECURSIVE DESCENT COMPARISON ROUTINE HERE
      # VODOO, BLACK MAGIC, SILVER BULLETS, DIVINE INTERVENTION
    }
  }

  return TRUE;
}
# }}}