Perl closure example and dispatch table

tags = #perl #programming

code=yes

http://stackoverflow.com/questions/4665268/perl-closures-and

http://perldoc.perl.org/perlfaq7.html#What's-a-closure%3f

http://www.perl.com/pub/2002/05/29/closure.html

From the Date::Formatter Perl module
http://search.cpan.org/dist/Date-Formatter/lib/Date/Formatter.pm


	my %_parser_table = (
		"MM" 	=> \&getNumericMonth,
		"M" 	=> \&getMonth,
		"DD" 	=> \&getDayOfMonth,
		"D" 	=> \&getDayOfWeek,
		"YY" 	=> \&getYear,
		"YYYY" 	=> \&getFullYear,
		"hh" 	=> \&getHours,
		"mm" 	=> \&getMinutes,
		"ss" 	=> \&getSeconds,
		"T" 	=> \&isAMorPM,
		"O"		=> \&getGMTOffset
	);

sub createDateFormatter {
		my ($self, $format, $pattern) = @_;
		my @date_format;
		$pattern ||= qr/\(|\)/;
		my @tokens = split $pattern => $format;
		while (@tokens) {
			my $token = shift(@tokens);
			if (exists $_parser_table{$token}) {
				push @date_format, $_parser_table{$token};
			}
			else {
				push @date_format, sub{ return "$token" };
			}
		}
		$self->{formatter} = sub {
			my ($self) = @_;
			return join "" => map {
				$_->($self);
			} @date_format;
		};
		return $self;
	}	


=======================

http://stackoverflow.com/questions/4665268/perl-closures-and

use strict;
use warnings;
use 5.010;
my @closures;
foreach my $_ (1..3) {
  # create some closures
  push @closures, sub { say "I will remember $_"; };
}
foreach (@closures) {
  # call the closures to see what they remember
  # the result is not obvious
  &{$_}();
}