#
# 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 .
#



###
### memoize-normalize3
###

## Chapter 3 section 7

sub memoize {
  my ($func, $keygen) = @_;
  $keygen ||= q{join ',', @_};

  my %cache;
  my $newcode = q{ 
    sub { my $key = do { KEYGEN };
          $cache{$key} = $func->(@_) unless exists $cache{$key};
          return $cache{$key};
        }
  };
  $newcode =~ s/KEYGEN/$keygen/g;
  return eval $newcode;
}