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The Sleep Scripting Project 2.1-b25 (Default branch)
05-09-2008
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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)