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57

copy_observers

       136  sub copy_observers {
       137      my ( $item_from, $item_to ) = @_;
       138      my @from_observers = $item_from->get_observers;
       139      foreach my $observer ( @from_observers ) {
       140          $item_to->add_observer( $observer );
       141      }
       142      return scalar @from_observers;
       143  }

• add_observer can be used to add multiple observers

• The author has apparently forgotten this

• Here's my version:

        sub copy_observers {
          my ($from, $to) = @_;
          $to->add_observer($from->get_observers);
        }

• I got the return value wrong here

• My version returns the new number of observers on $to

• Apparently it was supposed to return the old number in $from

• Why?????

• Fortunately, the test suite failed to detect this, so I ignored it

• Thus sparing all of you a big noisy rant about inane function return values

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