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Revision 1.35 by root, Mon Sep 24 00:16:30 2001 UTC vs.
Revision 1.178 by root, Thu Apr 17 22:33:10 2008 UTC

6 6
7 use Coro; 7 use Coro;
8 8
9 async { 9 async {
10 # some asynchronous thread of execution 10 # some asynchronous thread of execution
11 print "2\n";
12 cede; # yield back to main
13 print "4\n";
11 }; 14 };
15 print "1\n";
16 cede; # yield to coroutine
17 print "3\n";
18 cede; # and again
12 19
13 # alternatively create an async process like this: 20 # use locking
21 my $lock = new Coro::Semaphore;
22 my $locked;
14 23
15 sub some_func : Coro { 24 $lock->down;
16 # some more async code 25 $locked = 1;
17 } 26 $lock->up;
18
19 cede;
20 27
21=head1 DESCRIPTION 28=head1 DESCRIPTION
22 29
23This module collection manages coroutines. Coroutines are similar to 30This module collection manages coroutines. Coroutines are similar
24Threads but don't run in parallel. 31to threads but don't run in parallel at the same time even on SMP
32machines. The specific flavor of coroutine used in this module also
33guarantees you that it will not switch between coroutines unless
34necessary, at easily-identified points in your program, so locking and
35parallel access are rarely an issue, making coroutine programming much
36safer than threads programming.
25 37
26This module is still experimental, see the BUGS section below. 38(Perl, however, does not natively support real threads but instead does a
39very slow and memory-intensive emulation of processes using threads. This
40is a performance win on Windows machines, and a loss everywhere else).
27 41
28In this module, coroutines are defined as "callchain + lexical variables 42In this module, coroutines are defined as "callchain + lexical variables +
29+ @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own 43@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
30callchain, it's own set of lexicals and it's own set of perl's most 44its own set of lexicals and its own set of perls most important global
31important global variables. 45variables (see L<Coro::State> for more configuration).
32 46
33=cut 47=cut
34 48
35package Coro; 49package Coro;
36 50
51use strict;
52no warnings "uninitialized";
53
37use Coro::State; 54use Coro::State;
38 55
39use base Exporter; 56use base qw(Coro::State Exporter);
40 57
58our $idle; # idle handler
59our $main; # main coroutine
60our $current; # current coroutine
61
41$VERSION = 0.5; 62our $VERSION = '4.51';
42 63
43@EXPORT = qw(async cede schedule terminate current); 64our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
44%EXPORT_TAGS = ( 65our %EXPORT_TAGS = (
45 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)], 66 prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
46); 67);
47@EXPORT_OK = @{$EXPORT_TAGS{prio}}; 68our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
48 69
49{ 70{
50 my @async; 71 my @async;
51 my $init; 72 my $init;
52 73
53 # this way of handling attributes simply is NOT scalable ;() 74 # this way of handling attributes simply is NOT scalable ;()
54 sub import { 75 sub import {
76 no strict 'refs';
77
55 Coro->export_to_level(1, @_); 78 Coro->export_to_level (1, @_);
79
56 my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE}; 80 my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
57 *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub { 81 *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
58 my ($package, $ref) = (shift, shift); 82 my ($package, $ref) = (shift, shift);
59 my @attrs; 83 my @attrs;
60 for (@_) { 84 for (@_) {
75 }; 99 };
76 } 100 }
77 101
78} 102}
79 103
104=over 4
105
80=item $main 106=item $main
81 107
82This coroutine represents the main program. 108This coroutine represents the main program.
83 109
84=cut 110=cut
85 111
86our $main = new Coro; 112$main = new Coro;
87 113
88=item $current (or as function: current) 114=item $current (or as function: current)
89 115
90The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course). 116The current coroutine (the last coroutine switched to). The initial value
117is C<$main> (of course).
91 118
119This variable is B<strictly> I<read-only>. It is provided for performance
120reasons. If performance is not essential you are encouraged to use the
121C<Coro::current> function instead.
122
92=cut 123=cut
124
125$main->{desc} = "[main::]";
93 126
94# maybe some other module used Coro::Specific before... 127# maybe some other module used Coro::Specific before...
95if ($current) {
96 $main->{specific} = $current->{specific}; 128$main->{_specific} = $current->{_specific}
97} 129 if $current;
98 130
99our $current = $main; 131_set_current $main;
100 132
101sub current() { $current } 133sub current() { $current }
102 134
103=item $idle 135=item $idle
104 136
105The coroutine to switch to when no other coroutine is running. The default 137A callback that is called whenever the scheduler finds no ready coroutines
106implementation prints "FATAL: deadlock detected" and exits. 138to run. The default implementation prints "FATAL: deadlock detected" and
139exits, because the program has no other way to continue.
107 140
108=cut 141This hook is overwritten by modules such as C<Coro::Timer> and
142C<Coro::Event> to wait on an external event that hopefully wake up a
143coroutine so the scheduler can run it.
109 144
110# should be done using priorities :( 145Please note that if your callback recursively invokes perl (e.g. for event
111our $idle = new Coro sub { 146handlers), then it must be prepared to be called recursively itself.
112 print STDERR "FATAL: deadlock detected\n"; 147
113 exit(51); 148=cut
149
150$idle = sub {
151 require Carp;
152 Carp::croak ("FATAL: deadlock detected");
114}; 153};
154
155sub _cancel {
156 my ($self) = @_;
157
158 # free coroutine data and mark as destructed
159 $self->_destroy
160 or return;
161
162 # call all destruction callbacks
163 $_->(@{$self->{_status}})
164 for @{(delete $self->{_on_destroy}) || []};
165}
115 166
116# this coroutine is necessary because a coroutine 167# this coroutine is necessary because a coroutine
117# cannot destroy itself. 168# cannot destroy itself.
118my @destroy; 169my @destroy;
170my $manager;
171
119my $manager = new Coro sub { 172$manager = new Coro sub {
120 while() { 173 while () {
121 delete ((pop @destroy)->{_coro_state}) while @destroy; 174 (shift @destroy)->_cancel
175 while @destroy;
176
122 &schedule; 177 &schedule;
123 } 178 }
124}; 179};
180$manager->desc ("[coro manager]");
181$manager->prio (PRIO_MAX);
125 182
126# static methods. not really. 183=back
127 184
128=head2 STATIC METHODS 185=head2 STATIC METHODS
129 186
130Static methods are actually functions that operate on the current process only. 187Static methods are actually functions that operate on the current coroutine only.
131 188
132=over 4 189=over 4
133 190
134=item async { ... } [@args...] 191=item async { ... } [@args...]
135 192
136Create a new asynchronous process and return it's process object 193Create a new asynchronous coroutine and return it's coroutine object
137(usually unused). When the sub returns the new process is automatically 194(usually unused). When the sub returns the new coroutine is automatically
138terminated. 195terminated.
196
197See the C<Coro::State::new> constructor for info about the coroutine
198environment in which coroutines run.
199
200Calling C<exit> in a coroutine will do the same as calling exit outside
201the coroutine. Likewise, when the coroutine dies, the program will exit,
202just as it would in the main program.
139 203
140 # create a new coroutine that just prints its arguments 204 # create a new coroutine that just prints its arguments
141 async { 205 async {
142 print "@_\n"; 206 print "@_\n";
143 } 1,2,3,4; 207 } 1,2,3,4;
144 208
145The coderef you submit MUST NOT be a closure that refers to variables
146in an outer scope. This does NOT work. Pass arguments into it instead.
147
148=cut 209=cut
149 210
150sub async(&@) { 211sub async(&@) {
151 my $pid = new Coro @_; 212 my $coro = new Coro @_;
152 $manager->ready; # this ensures that the stack is cloned from the manager
153 $pid->ready; 213 $coro->ready;
154 $pid; 214 $coro
215}
216
217=item async_pool { ... } [@args...]
218
219Similar to C<async>, but uses a coroutine pool, so you should not call
220terminate or join (although you are allowed to), and you get a coroutine
221that might have executed other code already (which can be good or bad :).
222
223Also, the block is executed in an C<eval> context and a warning will be
224issued in case of an exception instead of terminating the program, as
225C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
226will not work in the expected way, unless you call terminate or cancel,
227which somehow defeats the purpose of pooling.
228
229The priority will be reset to C<0> after each job, tracing will be
230disabled, the description will be reset and the default output filehandle
231gets restored, so you can change alkl these. Otherwise the coroutine will
232be re-used "as-is": most notably if you change other per-coroutine global
233stuff such as C<$/> you need to revert that change, which is most simply
234done by using local as in C< local $/ >.
235
236The pool size is limited to 8 idle coroutines (this can be adjusted by
237changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
238required.
239
240If you are concerned about pooled coroutines growing a lot because a
241single C<async_pool> used a lot of stackspace you can e.g. C<async_pool
242{ terminate }> once per second or so to slowly replenish the pool. In
243addition to that, when the stacks used by a handler grows larger than 16kb
244(adjustable with $Coro::POOL_RSS) it will also exit.
245
246=cut
247
248our $POOL_SIZE = 8;
249our $POOL_RSS = 16 * 1024;
250our @async_pool;
251
252sub pool_handler {
253 my $cb;
254
255 while () {
256 eval {
257 while () {
258 _pool_1 $cb;
259 &$cb;
260 _pool_2 $cb;
261 &schedule;
262 }
263 };
264
265 last if $@ eq "\3async_pool terminate\2\n";
266 warn $@ if $@;
267 }
268}
269
270sub async_pool(&@) {
271 # this is also inlined into the unlock_scheduler
272 my $coro = (pop @async_pool) || new Coro \&pool_handler;
273
274 $coro->{_invoke} = [@_];
275 $coro->ready;
276
277 $coro
155} 278}
156 279
157=item schedule 280=item schedule
158 281
159Calls the scheduler. Please note that the current process will not be put 282Calls the scheduler. Please note that the current coroutine will not be put
160into the ready queue, so calling this function usually means you will 283into the ready queue, so calling this function usually means you will
161never be called again. 284never be called again unless something else (e.g. an event handler) calls
285ready.
162 286
163=cut 287The canonical way to wait on external events is this:
288
289 {
290 # remember current coroutine
291 my $current = $Coro::current;
292
293 # register a hypothetical event handler
294 on_event_invoke sub {
295 # wake up sleeping coroutine
296 $current->ready;
297 undef $current;
298 };
299
300 # call schedule until event occurred.
301 # in case we are woken up for other reasons
302 # (current still defined), loop.
303 Coro::schedule while $current;
304 }
164 305
165=item cede 306=item cede
166 307
167"Cede" to other processes. This function puts the current process into the 308"Cede" to other coroutines. This function puts the current coroutine into the
168ready queue and calls C<schedule>, which has the effect of giving up the 309ready queue and calls C<schedule>, which has the effect of giving up the
169current "timeslice" to other coroutines of the same or higher priority. 310current "timeslice" to other coroutines of the same or higher priority.
170 311
171=cut 312=item Coro::cede_notself
172 313
314Works like cede, but is not exported by default and will cede to any
315coroutine, regardless of priority, once.
316
173=item terminate 317=item terminate [arg...]
174 318
175Terminates the current process. 319Terminates the current coroutine with the given status values (see L<cancel>).
176 320
177Future versions of this function will allow result arguments. 321=item killall
322
323Kills/terminates/cancels all coroutines except the currently running
324one. This is useful after a fork, either in the child or the parent, as
325usually only one of them should inherit the running coroutines.
178 326
179=cut 327=cut
180 328
181sub terminate { 329sub terminate {
182 $current->cancel; 330 $current->cancel (@_);
183 &schedule; 331}
184 die; # NORETURN 332
333sub killall {
334 for (Coro::State::list) {
335 $_->cancel
336 if $_ != $current && UNIVERSAL::isa $_, "Coro";
337 }
185} 338}
186 339
187=back 340=back
188 341
189# dynamic methods
190
191=head2 PROCESS METHODS 342=head2 COROUTINE METHODS
192 343
193These are the methods you can call on process objects. 344These are the methods you can call on coroutine objects.
194 345
195=over 4 346=over 4
196 347
197=item new Coro \&sub [, @args...] 348=item new Coro \&sub [, @args...]
198 349
199Create a new process and return it. When the sub returns the process 350Create a new coroutine and return it. When the sub returns the coroutine
200automatically terminates. To start the process you must first put it into 351automatically terminates as if C<terminate> with the returned values were
352called. To make the coroutine run you must first put it into the ready queue
201the ready queue by calling the ready method. 353by calling the ready method.
202 354
203The coderef you submit MUST NOT be a closure that refers to variables 355See C<async> and C<Coro::State::new> for additional info about the
204in an outer scope. This does NOT work. Pass arguments into it instead. 356coroutine environment.
205 357
206=cut 358=cut
207 359
208sub _newcoro { 360sub _run_coro {
209 terminate &{+shift}; 361 terminate &{+shift};
210} 362}
211 363
212sub new { 364sub new {
213 my $class = shift; 365 my $class = shift;
214 bless {
215 _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
216 }, $class;
217}
218 366
219=item $process->ready 367 $class->SUPER::new (\&_run_coro, @_)
368}
220 369
221Put the current process into the ready queue. 370=item $success = $coroutine->ready
222 371
223=cut 372Put the given coroutine into the ready queue (according to it's priority)
373and return true. If the coroutine is already in the ready queue, do nothing
374and return false.
224 375
225=item $process->cancel 376=item $is_ready = $coroutine->is_ready
226 377
227Like C<terminate>, but terminates the specified process instead. 378Return wether the coroutine is currently the ready queue or not,
379
380=item $coroutine->cancel (arg...)
381
382Terminates the given coroutine and makes it return the given arguments as
383status (default: the empty list). Never returns if the coroutine is the
384current coroutine.
228 385
229=cut 386=cut
230 387
231sub cancel { 388sub cancel {
389 my $self = shift;
390 $self->{_status} = [@_];
391
392 if ($current == $self) {
232 push @destroy, $_[0]; 393 push @destroy, $self;
233 $manager->ready; 394 $manager->ready;
234 &schedule if $current == $_[0]; 395 &schedule while 1;
396 } else {
397 $self->_cancel;
398 }
235} 399}
236 400
401=item $coroutine->join
402
403Wait until the coroutine terminates and return any values given to the
404C<terminate> or C<cancel> functions. C<join> can be called concurrently
405from multiple coroutines.
406
407=cut
408
409sub join {
410 my $self = shift;
411
412 unless ($self->{_status}) {
413 my $current = $current;
414
415 push @{$self->{_on_destroy}}, sub {
416 $current->ready;
417 undef $current;
418 };
419
420 &schedule while $current;
421 }
422
423 wantarray ? @{$self->{_status}} : $self->{_status}[0];
424}
425
426=item $coroutine->on_destroy (\&cb)
427
428Registers a callback that is called when this coroutine gets destroyed,
429but before it is joined. The callback gets passed the terminate arguments,
430if any.
431
432=cut
433
434sub on_destroy {
435 my ($self, $cb) = @_;
436
437 push @{ $self->{_on_destroy} }, $cb;
438}
439
237=item $oldprio = $process->prio($newprio) 440=item $oldprio = $coroutine->prio ($newprio)
238 441
239Sets the priority of the process. Higher priority processes get run before 442Sets (or gets, if the argument is missing) the priority of the
240lower priority processes. Priorities are smalled signed integer (currently 443coroutine. Higher priority coroutines get run before lower priority
444coroutines. Priorities are small signed integers (currently -4 .. +3),
241-4 .. +3), that you can refer to using PRIO_xxx constants (use the import 445that you can refer to using PRIO_xxx constants (use the import tag :prio
242tag :prio to get then): 446to get then):
243 447
244 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN 448 PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
245 3 > 1 > 0 > -1 > -3 > -4 449 3 > 1 > 0 > -1 > -3 > -4
246 450
247 # set priority to HIGH 451 # set priority to HIGH
248 current->prio(PRIO_HIGH); 452 current->prio(PRIO_HIGH);
249 453
250The idle coroutine ($Coro::idle) always has a lower priority than any 454The idle coroutine ($Coro::idle) always has a lower priority than any
251existing coroutine. 455existing coroutine.
252 456
253Changing the priority of the current process will take effect immediately, 457Changing the priority of the current coroutine will take effect immediately,
254but changing the priority of processes in the ready queue (but not 458but changing the priority of coroutines in the ready queue (but not
255running) will only take effect after the next schedule (of that 459running) will only take effect after the next schedule (of that
256process). This is a bug that will be fixed in some future version. 460coroutine). This is a bug that will be fixed in some future version.
257 461
258=cut
259
260sub prio {
261 my $old = $_[0]{prio};
262 $_[0]{prio} = $_[1] if @_ > 1;
263 $old;
264}
265
266=item $newprio = $process->nice($change) 462=item $newprio = $coroutine->nice ($change)
267 463
268Similar to C<prio>, but subtract the given value from the priority (i.e. 464Similar to C<prio>, but subtract the given value from the priority (i.e.
269higher values mean lower priority, just as in unix). 465higher values mean lower priority, just as in unix).
270 466
271=cut 467=item $olddesc = $coroutine->desc ($newdesc)
272 468
273sub nice { 469Sets (or gets in case the argument is missing) the description for this
274 $_[0]{prio} -= $_[1]; 470coroutine. This is just a free-form string you can associate with a coroutine.
471
472This method simply sets the C<< $coroutine->{desc} >> member to the given string. You
473can modify this member directly if you wish.
474
475=item $coroutine->throw ([$scalar])
476
477If C<$throw> is specified and defined, it will be thrown as an exception
478inside the coroutine at the next convinient point in time (usually after
479it gains control at the next schedule/transfer/cede). Otherwise clears the
480exception object.
481
482The exception object will be thrown "as is" with the specified scalar in
483C<$@>, i.e. if it is a string, no line number or newline will be appended
484(unlike with C<die>).
485
486This can be used as a softer means than C<cancel> to ask a coroutine to
487end itself, although there is no guarentee that the exception will lead to
488termination, and if the exception isn't caught it might well end the whole
489program.
490
491=cut
492
493sub desc {
494 my $old = $_[0]{desc};
495 $_[0]{desc} = $_[1] if @_ > 1;
496 $old;
275} 497}
276 498
277=back 499=back
278 500
501=head2 GLOBAL FUNCTIONS
502
503=over 4
504
505=item Coro::nready
506
507Returns the number of coroutines that are currently in the ready state,
508i.e. that can be switched to. The value C<0> means that the only runnable
509coroutine is the currently running one, so C<cede> would have no effect,
510and C<schedule> would cause a deadlock unless there is an idle handler
511that wakes up some coroutines.
512
513=item my $guard = Coro::guard { ... }
514
515This creates and returns a guard object. Nothing happens until the object
516gets destroyed, in which case the codeblock given as argument will be
517executed. This is useful to free locks or other resources in case of a
518runtime error or when the coroutine gets canceled, as in both cases the
519guard block will be executed. The guard object supports only one method,
520C<< ->cancel >>, which will keep the codeblock from being executed.
521
522Example: set some flag and clear it again when the coroutine gets canceled
523or the function returns:
524
525 sub do_something {
526 my $guard = Coro::guard { $busy = 0 };
527 $busy = 1;
528
529 # do something that requires $busy to be true
530 }
531
532=cut
533
534sub guard(&) {
535 bless \(my $cb = $_[0]), "Coro::guard"
536}
537
538sub Coro::guard::cancel {
539 ${$_[0]} = sub { };
540}
541
542sub Coro::guard::DESTROY {
543 ${$_[0]}->();
544}
545
546
547=item unblock_sub { ... }
548
549This utility function takes a BLOCK or code reference and "unblocks" it,
550returning the new coderef. This means that the new coderef will return
551immediately without blocking, returning nothing, while the original code
552ref will be called (with parameters) from within its own coroutine.
553
554The reason this function exists is that many event libraries (such as the
555venerable L<Event|Event> module) are not coroutine-safe (a weaker form
556of thread-safety). This means you must not block within event callbacks,
557otherwise you might suffer from crashes or worse.
558
559This function allows your callbacks to block by executing them in another
560coroutine where it is safe to block. One example where blocking is handy
561is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
562disk.
563
564In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
565creating event callbacks that want to block.
566
567=cut
568
569our @unblock_queue;
570
571# we create a special coro because we want to cede,
572# to reduce pressure on the coro pool (because most callbacks
573# return immediately and can be reused) and because we cannot cede
574# inside an event callback.
575our $unblock_scheduler = new Coro sub {
576 while () {
577 while (my $cb = pop @unblock_queue) {
578 # this is an inlined copy of async_pool
579 my $coro = (pop @async_pool) || new Coro \&pool_handler;
580
581 $coro->{_invoke} = $cb;
582 $coro->ready;
583 cede; # for short-lived callbacks, this reduces pressure on the coro pool
584 }
585 schedule; # sleep well
586 }
587};
588$unblock_scheduler->desc ("[unblock_sub scheduler]");
589
590sub unblock_sub(&) {
591 my $cb = shift;
592
593 sub {
594 unshift @unblock_queue, [$cb, @_];
595 $unblock_scheduler->ready;
596 }
597}
598
599=back
600
279=cut 601=cut
280 602
2811; 6031;
282 604
283=head1 BUGS/LIMITATIONS 605=head1 BUGS/LIMITATIONS
284 606
285 - you must make very sure that no coro is still active on global destruction. 607 - you must make very sure that no coro is still active on global
286 very bad things might happen otherwise (usually segfaults). 608 destruction. very bad things might happen otherwise (usually segfaults).
609
287 - this module is not thread-safe. You must only ever use this module from 610 - this module is not thread-safe. You should only ever use this module
288 the same thread (this requirement might be loosened in the future to 611 from the same thread (this requirement might be loosened in the future
289 allow per-thread schedulers, but Coro::State does not yet allow this). 612 to allow per-thread schedulers, but Coro::State does not yet allow
613 this).
290 614
291=head1 SEE ALSO 615=head1 SEE ALSO
292 616
293L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>, 617Lower level Configuration, Coroutine Environment: L<Coro::State>.
294L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>, 618
295L<Coro::Handle>, L<Coro::Socket>. 619Debugging: L<Coro::Debug>.
620
621Support/Utility: L<Coro::Specific>, L<Coro::Util>.
622
623Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
624
625Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>.
626
627Compatibility: L<Coro::LWP>, L<Coro::Storable>, L<Coro::Select>.
628
629Embedding: L<Coro::MakeMaker>.
296 630
297=head1 AUTHOR 631=head1 AUTHOR
298 632
299 Marc Lehmann <pcg@goof.com> 633 Marc Lehmann <schmorp@schmorp.de>
300 http://www.goof.com/pcg/marc/ 634 http://home.schmorp.de/
301 635
302=cut 636=cut
303 637

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