NAME

       "CPS::Governor::Deferred" - iterate at some later point

SYNOPSIS

        use CPS qw( gkforeach );
        use CPS::Governor::Deferred;

        my $gov = CPS::Governor::Deferred->new;

        gkforeach( $gov, [ 1 .. 10 ],
           sub {
              my ( $item, $knext ) = @_;

              print "A$item ";
              goto &$knext;
           },
           sub {},
        );

        gkforeach( $gov, [ 1 .. 10 ],
           sub {
              my ( $item, $knext ) = @_;

              print "B$item ";
              goto &$knext;
           },
           sub {},
        );

        $gov->flush;

DESCRIPTION

       This CPS::Governor allows the functions using it to delay their iteration until some later
       point when the containing program invokes it. This allows two main advantages:

       •   CPU-intensive operations may be split apart and mixed with other IO operations

       •   Multiple control functions may be executed in pseudo-parallel, interleaving iterations
           of each giving a kind of concurrency

       These are achieved by having the governor store a list of code references that need to be
       invoked, rather than invoking them immediately. These references can then be invoked
       later, perhaps by using an idle watcher in an event framework.

       Because each code reference hasn't yet been invoked by the time the "again" method is
       called, the original caller is free to store more pending references with the governor.
       This allows multiple control functions to be interleaved, as in the "A" and "B" example
       above.

CONSTRUCTOR

   $gov = CPS::Governor::Deferred->new( %args )
       Returns a new instance of a "CPS::Governor::Deferred" object. Requires no parameters but
       may take any of the following to adjust its default behaviour:

       defer_after => INT
               If given some positive number, $n then the first "$n-1" invocations of the "again"
               method will in fact be executed immediately. Thereafter they will be enqueued in
               the normal mechanism. This gives the effect that longrunning loops will be
               executed in batches of $n.

               If not supplied then every invocation of "again" will use the queueing mechanism.

METHODS

   $pending = $gov->is_pending
       Returns true if at least one code reference has been stored that hasn't yet been invoked.

   $gov->prod
       Invokes all of the currently-stored code references, in the order they were stored. If any
       new references are stored by these, they will not yet be invoked, but will be available
       for the next time this method is called.

   $gov->flush
       Repeatedly calls "prod" until no more code references are pending.

SUBCLASS METHODS

       The following methods are used internally to implement the functionality, which may be
       useful to implementors of subclasses.

   $gov->later( $code, @args )
       Used to enqueue the $code ref to be invoked later with the given @args, once it is
       determined this should be deferred (rather than being invoked immediately in the case of
       the first few invocations when "defer_after" is set).

AUTHOR

       Paul Evans <leonerd@leonerd.org.uk>