#
# This software is Copyright 2005 by Elsevier Inc.  You may use it
# under the terms of the license at http://perl.plover.com/hop/LICENSE.txt .
#



###
### fib-cached
###

## Chapter 3 section 2

# Compute the number of pairs of rabbits alive in month n
{ my %cache;
  sub fib {
    my ($month) = @_;
    unless (exists $cache{$month}) {
      if ($month < 2) { $cache{$month} = 1 }
      else {
        $cache{$month} = fib($month-1) + fib($month-2);
      }
    } 
    return $cache{$month};
  }
}