CPS::Governor(3pm)					User Contributed Perl Documentation					CPS::Governor(3pm)

NAME

       "CPS::Governor" - control the iteration of the "CPS" functions

DESCRIPTION

       Objects based on this abstract class are used by the "gk*" variants of the CPS functions, to control their behavior. These objects are
       expected to provide a method, "again", which the functions will use to re-invoke iterations of loops, and so on. By providing a different
       implementation of this method, governor objects can provide such behaviours as rate-limiting, asynchronisation or parallelism, and
       integration with event-based IO frameworks.

CONSTRUCTOR

   $gov = CPS::Governor->new
       Must be called on a subclass which implements the "again" method. Returns a new instance of a governor object in that class.

SUBCLASS METHODS

       Because this is an abstract class, instances of it can only be constructed on a subclass which implements the following methods:

   $gov->again( $code, @args )
       Execute the function given in the "CODE" reference $code, passing in the arguments @args. If this is going to be executed immediately, it
       should be invoked using a tail-call directly by the "again" method, so that the stack does not grow arbitrarily. This can be achieved by,
       for example:

	@_ = @args;
	goto &$code;

       Alternatively, the Sub::Call::Tail may be used to apply syntactic sugar, allowing you to write instead:

	use Sub::Call::Tail;
	...
	tail $code->( @args );

EXAMPLES

   A Governor With A Time Delay
       Consider the following subclass, which implements a "CPS::Governor" subclass that calls "sleep()" between every invocation.

	package Governor::Sleep

	use base qw( CPS::Governor );

	sub new
	{
	   my $class = shift;
	   my ( $delay ) = @_;

	   my $self = $class->SUPER::new;
	   $self->{delay} = $delay;

	   return $self;
	}

	sub again
	{
	   my $self = shift;
	   my $code = shift;

	   sleep $self->{delay};

	   # @args are still in @_
	   goto &$code;
	}

SEE ALSO

       o   Sub::Call::Tail - Tail calls for subroutines and methods

AUTHOR

       Paul Evans <leonerd@leonerd.org.uk>

perl v5.14.2							    2012-06-27							CPS::Governor(3pm)