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.\" ========================================================================
.\"
.IX Title "Future::Queue 3pm"
.TH Future::Queue 3pm "2022-01-28" "perl v5.32.1" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.SH "NAME"
"Future::Queue" \- a FIFO queue of values that uses Futures
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\&   use Future::Queue;
\&
\&   my $queue = Future::Queue\->new;
\&
\&   my $f = repeat {
\&      $queue\->shift\->then(sub {
\&         my ( $thing ) = @_;
\&         ...
\&      });
\&   };
\&
\&   $queue\->push( "a thing" );
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
Objects in this class provide a simple \s-1FIFO\s0 queue the stores arbitrary perl
values. Values may be added into the queue using the \*(L"push\*(R" method, and
retrieved from it using the \*(L"shift\*(R" method.
.PP
Values may be stored within the queue object for \f(CW\*(C`shift\*(C'\fR to retrieve later,
or if the queue is empty then the future that \f(CW\*(C`shift\*(C'\fR returns will be
completed once an item becomes available.
.SH "CONSTRUCTOR"
.IX Header "CONSTRUCTOR"
.SS "new"
.IX Subsection "new"
.Vb 1
\&   $queue = Future::Queue\->new
.Ve
.PP
Returns a new \f(CW\*(C`Future::Queue\*(C'\fR instance.
.SS "push"
.IX Subsection "push"
.Vb 1
\&   $queue\->push( $item )
.Ve
.PP
Adds a new item into the queue. If the queue was previously empty and there is
at least one \f(CW\*(C`shift\*(C'\fR future waiting, then the next one will be completed by
this method.
.SS "shift"
.IX Subsection "shift"
.Vb 1
\&   $item = $queue\->shift\->get
.Ve
.PP
Returns a \f(CW\*(C`Future\*(C'\fR that will yield the next item from the queue. If there is
already an item then this will be taken and the returned future will be
immediate. If not, then the returned future will be pending, and the next
\&\f(CW\*(C`push\*(C'\fR method will complete it.
.SH "AUTHOR"
.IX Header "AUTHOR"
Paul Evans <leonerd@leonerd.org.uk>