#
# 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-normalize2
###

## Chapter 3 section 7

sub memoize {
  my ($func, $keygen) = @_;
  my %cache;
  my $stub = $keygen ? 
    sub { my $key = $keygen->(@_);
          $cache{$key} = $func->(@_) unless exists $cache{$key};
          return $cache{$key};
        }
  :
    sub { my $key = join ',', @_;
          $cache{$key} = $func->(@_) unless exists $cache{$key};
          return $cache{$key};
        }
  ;
  return $stub;
}