Iterator Operations

• If the iterator returns the list items in some canonical order, you can do this:

 my $both = both($it1, $it2);
 $item = $both->(); # get next item from $it1 or $it2

 # Get rest of items in appropriate order
 while (defined($item = $both->())) {
 #...
 }

• The both function works for any iterators

• If an iterator represents a database query, this is the OR operation

  • Straightforward implementation on next slide

  • AND is a little harder, but not much