in reply to RFC: Practical closure example: Spreadsheet writer

Thanks for writing this - I found it interesting. I recently needed to write something that ended up including the first practical use of a closure that I've ever done - I needed to be able to look up a value from a hash table many times, in several different subroutines, but I didn't want to either (a) make the hash global, or (b) have the hash reloaded in each sub.

It was the first time I realized that, hey, closures could be quite useful (my example below). 

my $monthConverter = monthConverterFactory();

...

my $moNum = &$monthConverter($mo);
   if ($moNum > $currentDate[1]) {
   $y = $currentDate[2] - 1;
}

...

# Use a closure here, so we don't have to load this private
# data more than once.
sub monthConverterFactory {
   my %months = ( Jan => 0,
      Feb => 1,
      Mar => 2,
      Apr => 3,
      May => 4,
      Jun => 5,
      Jul => 6,
      Aug => 7,
      Sep => 8,
      Oct => 9,
      Nov => 10,
      Dec => 11 
   );
   return sub {
      my $val = shift;
      return $months{$val};
   }
}

[download]

In Section Meditations