class Supply

Asynchronous data stream with multiple subscribers

class Supply {}

A supply is a thread-safe, asynchronous data stream like a Channel, but it can have multiple subscribers (taps) that all get the same values flowing through the supply.

It is a thread-safe implementation of the Observer Pattern, and central to supporting reactive programming in Perl 6.

There are two types of Supplies: live and on demand. When tapping into a live supply, the tap will only see values that are flowing through the supply after the tap has been created. Such supplies are normally infinite in nature, such as mouse movements. Closing such a tap does not stop mouse events from occurring, it just means that the values will go by unseen. All tappers see the same flow of values.

A tap on an on demand supply will initiate the production of values, and tapping the supply again may result in a new set of values. For example, Supply.interval produces a fresh timer with the appropriate interval each time it is tapped. If the tap is closed, the timer simply stops emitting values to that tap.

A live Supply is obtained from the Supplier factory method Supply. New values are emitted by calling emit on the Supplier object.

my $supplier =;
my $supply = $supplier.Supply;
$supply.tap(-> $v { say "$v" });
$supplier.emit(42); # Will cause the tap to output "42" 

The live method returns True on live supplies. Factory methods such as interval, from-list will return on demand supplies.

A live Supply that keeps values until tapped the first time can be created with Supplier::Preserving.

Further examples can be found in the concurrency page.

Methods that return Taps

method tap

method tap(Supply:D: &emit = -> $ { },
    --> Tap:D)

Creates a new tap (a kind of subscription if you will), in addition to all existing taps. The first positional argument is a piece of code that will be called when a new value becomes available through the emit call.

The &done callback is called when the done method on the supply is called, indicating the end of life of the channel. For a live supply the done routine will be called on the parent Supplier.

The &quit callback is called when the quit method on the supply is called, indicating an erroneous termination of the supply. For a live supply the quit routine will be called on the parent Supplier

Method tap returns an object of type Tap, on which you can call the close method to cancel the subscription.

my $s = Supply.from-list(0 .. 5);
my $t = $s.tap(-> $v { say $v }done => { say "no more ticks" });


no more ticks

method act

method act(Supply:D: &act --> Tap:D)

Creates a tap on the given supply with the given code. Differently from tap, the given code is guaranteed to be only executed by one thread at a time.

Utility methods

method Capture

Defined as:

method Capture(Supply:D --> Capture:D)

Equivalent to calling .List.Capture on the invocant.

method Channel

method Channel(Supply:D: --> Channel:D)

Returns a Channel object that will receive all future values from the supply, and will be closed when the Supply is done, and quit (shut down with error) when the supply is quit.

method Promise

method Promise(Supply:D: --> Promise:D)

Returns a Promise that will be kept when the Supply is done. If the Supply also emits any values, then the Promise will be kept with the final value. Otherwise, it will be kept with Nil. If the Supply ends with a quit instead of a done, then the Promise will be broken with that exception.

my $supplier =;
my $s = $supplier.Supply;
my $p = $s.Promise;
$p.then(-> $v { say "got $v.result()" });
$supplier.emit('cha');         # not output yet 
$supplier.done();              # got cha 

The Promise method is most useful when dealing with supplies that will tend to produce just one value, when only the final value is of interest, or when only completion (successful or not) is relevant.

method live

method live(Supply:D: --> Bool:D)

Returns True if the supply is "live", that is, values are emitted to taps as soon as they arrive. Always returns True in the default Supply (but for example on the supply returned from Supply.from-list it's False).

say;    # OUTPUT: «True␤» 

method schedule-on

method schedule-on(Supply:D: Scheduler $scheduler)

Runs the emit, done and quit callbacks on the specified scheduler.

This is useful for GUI toolkits that require certain actions to be run from the GUI thread.

Methods that wait until the supply is done

method wait

method wait(Supply:D:)

Taps the Supply it is called on, and blocks execution until the either the supply is done (in which case it evaluates to the final value that was emitted on the Supply, or Nil if not value was emitted) or quit (in which case it will throw the exception that was passed to quit).

my $s =;
start {
  sleep 1;
  say "One second: running.";
  sleep 1;
say "Two seconds: done";

method list

method list(Supply:D: --> List:D)

Taps the Supply it is called on, and returns a lazy list that will be reified as the Supply emits values. The list will be terminated once the Supply is done. If the Supply quits, then an exception will be thrown once that point in the lazy list is reached.

method grab

method grab(Supply:D: &when-done --> Supply:D)

Taps the Supply it is called on. When it is done, calls &when-done and then emits the list of values that it returns on the result Supply. If the original Supply quits, then the exception is immediately conveyed on the return Supply.

my $s = Supply.from-list(41032);
my $t = $s.grab(&sum);
$t.tap(&say);           # OUTPUT: «19␤» 

method reverse

method reverse(Supply:D: --> Supply:D)

Taps the Supply it is called on. Once that Supply emits done, all of the values it emitted will be emitted on the returned Supply in reverse order. If the original Supply quits, then the exception is immediately conveyed on the return Supply.

my $s = Supply.from-list(123);
my $t = $s.reverse;
$t.tap(&say);           # OUTPUT: «3␤2␤1␤» 

method sort

method sort(Supply:D: &custom-routine-to-use? --> Supply:D)

Taps the Supply it is called on. Once that Supply emits done, all of the values that it emitted will be sorted, and the results emitted on the returned Supply in the sorted order. Optionally accepts a comparator Block. If the original Supply quits, then the exception is immediately conveyed on the return Supply.

my $s = Supply.from-list(41032);
my $t = $s.sort();
$t.tap(&say);           # OUTPUT: «2␤3␤4␤10␤» 

Methods that return another Supply

method from-list

method from-list(Supply:U: +@values --> Supply:D)

Creates an on-demand supply from the values passed to this method.

my $s = Supply.from-list(123);
$s.tap(&say);           # OUTPUT: «1␤2␤3␤» 

method share

method share(Supply:D: --> Supply:D)

Creates a live supply from an on-demand supply, thus making it possible to share the values of the on-demand supply on multiple taps, instead of each tap seeing its own copy of all values from the on-demand supply.

# this says in turn: "first 1" "first 2" "second 2" "first 3" "second 3" 
my $s = Supply.interval(1).share;
$s.tap: { "first $_".say };
sleep 1.1;
$s.tap: { "second $_".say };
sleep 2

method flat

method flat(Supply:D: --> Supply:D)

Creates a supply on which all of the values seen in the given supply are flattened before being emitted again.

method do

method do(Supply:D: &do --> Supply:D)

Creates a supply to which all values seen in the given supply, are emitted again. The given code, executed for its side-effects only, is guaranteed to be only executed by one thread at a time.

method on-close

method on-close(Supply:D: &on-close --> Supply:D)

Returns a new Supply which will run &on-close whenever a Tap of that Supply is closed. This includes if further operations are chained on to the Supply. (for example, $supply.on-close(&on-close).map(*.uc)). When using a react or supply block, using the CLOSE phaser is usually a better choice.

my $s =;
my $tap = $s.Supply.on-close({ say "Tap closed" }).tap(
    -> $v { say "the value is $v" },
    done    => { say "Supply is done" },
    quit    => -> $ex { say "Supply finished with error $ex" },
$s.emit('Perl 6');
$tap.close;        # OUTPUT: «Tap closed␤» 

method interval

method interval(Supply:U: $interval$delay = 0:$scheduler = $*SCHEDULER --> Supply:D)

Creates a supply that emits a value every $interval seconds, starting $delay seconds from the call. The emitted value is an integer, starting from 0, and is incremented by one for each value emitted.

Implementations may treat too-small values as lowest resolution they support, possibly warning in such situations; e.g. treating 0.0001 as 0.001.

method grep

method grep(Supply:D: Mu $test --> Supply:D)

Creates a new supply that only emits those values from the original supply that smart-match against $test.

my $supplier =;
my $all      = $supplier.Supply;
my $ints     = $all.grep(Int);
$supplier.emit($_for 1'a string'3.14159;   # prints only 1 

method map

method map(Supply:D: &mapper --> Supply:D)

Returns a new supply that maps each value of the given supply through &mapper and emits it to the new supply.

my $supplier =;
my $all      = $supplier.Supply;
my $double   = $> $value { $value * 2 });
$supplier.emit(4);           # RESULT: «8» 

method batch

method batch(Supply:D: :$elems:$seconds --> Supply:D)

Creates a new supply that batches the values of the given supply by either the number of elements in the batch (using :elems) or the maximum number of seconds (using the :seconds) or both. Any remaining values are emitted in a final batch when the supply is done.

method elems

method elems(Supply:D: $seconds? --> Supply:D)

Creates a new supply in which changes to the number of values seen are emitted. It optionally also takes an interval (in seconds) if you only want to be updated every so many seconds.

method head

method head(Supply:D: Int(Cool$number = 1 --> Supply:D)

Creates a "head" supply with the same semantics as List.head.

my $s = Supply.from-list(41032);
my $hs = $s.head(2);
$hs.tap(&say);           # OUTPUT: «4␤10␤» 

method tail

method tail(Supply:D: Int(Cool$number = 1 --> Supply:D)

Creates a "tail" supply with the same semantics as List.tail.

my $s = Supply.from-list(41032);
my $ts = $s.tail(2);
$ts.tap(&say);           # OUTPUT: «3␤2␤» 

method rotor

method rotor(Supply:D: @cycle --> Supply:D)

Creates a "rotoring" supply with the same semantics as List.rotor.

method delayed

method delayed(Supply:D: $seconds:$scheduler = $*SCHEDULER --> Supply:D)

Creates a new supply in which all values flowing through the given supply are emitted, but with the given delay in seconds.

method throttle

method throttle(Supply:D:
  $limit,                 # values / time or simultaneous processing 
  $seconds or $callable,  # time-unit / code to process simultaneously 
  $delay = 0,             # initial delay before starting, in seconds 
  :$control,              # supply to emit control messages on (optional) 
  :$status,               # supply to tap status messages from (optional) 
  :$bleed,                # supply to bleed messages to (optional) 
  :$vent-at,              # bleed when so many buffered (optional) 
  :$scheduler,            # scheduler to use, default $*SCHEDULER 
  --> Supply:D)

Produces a Supply from a given Supply, but makes sure the number of messages passed through, is limited.

It has two modes of operation: per time-unit or by maximum number of execution of a block of code: this is determined by the second positional parameter.

The first positional parameter specifies the limit that should be applied.

If the second positional parameter is a Callable, then the limit indicates the maximum number of parallel processes executing the Callable, which is given the value that was received. The emitted values in this case will be the Promises that were obtained from starting the Callable.

If the second positional parameter is a numeric value, it is interpreted as the time-unit (in seconds). If you specify .1 as the value, then it makes sure you don't exceed the limit for every tenth of a second.

If the limit is exceeded, then incoming messages are buffered until there is room to pass on / execute the Callable again.

The third positional parameter is optional: it indicates the number of seconds the throttle will wait before passing on any values.

The :control named parameter optionally specifies a Supply that you can use to control the throttle while it is in operation. Messages that can be sent, are strings in the form of "key:value". Please see below for the types of messages that you can send to control the throttle.

The :status named parameter optionally specifies a Supply that will receive any status messages. If specified, it will at least send one status message after the original Supply is exhausted. See status message below.

The :bleed named parameter optionally specifies a Supply that will receive any values that were either explicitly bled (with the bleed control message), or automatically bled (if there's a vent-at active).

The :vent-at named parameter indicates the number of values that may be buffered before any additional value will be routed to the :bleed Supply. Defaults to 0 if not specified (causing no automatic bleeding to happen). Only makes sense if a :bleed Supply has also been specified.

The :scheduler named parameter indicates the scheduler to be used. Defaults to $*SCHEDULER.

control messages

These messages can be sent to the :control Supply. A control message consists of a string of the form "key: value", e.g. "limit: 4".

Change the number of messages (as initially given in the first positional) to the value given.

Route the given number of buffered messages to the :bleed Supply.

Change the maximum number of buffered values before automatic bleeding takes place. If the value is lower than before, will cause immediate rerouting of buffered values to match the new maximum.

Send a status message to the :status Supply with the given id.

status message

The status return message is a hash with the following keys:

The current number of messages / callables that is still allowed to be passed / executed.

The number of messages routed to the :bleed Supply.

The number of messages currently buffered because of overflow.

The number of messages emitted (passed through).

The id of this status message (a monotonically increasing number). Handy if you want to log status messages.

The current limit that is being applied.

The maximum number of messages that may be buffered before they're automatically re-routed to the :bleed Supply.


Have a simple piece of code announce when it starts running asynchronously, wait a random amount of time, then announce when it is done. Do this 6 times, but don't let more than 3 of them run simultaneously.

my $s = Supply.from-list(^6);  # set up supply 
my $t = $s.throttle: 3,        # only allow 3 at a time 
{                              # code block to run 
    say "running $_";          # announce we've started 
    sleep rand;                # wait some random time 
    say "done $_"              # announce we're done 
}                              # don't need ; because } at end of line 
$t.wait;                       # wait for the supply to be done 

and the result of one run will be:

running 0
running 1
running 2
done 2
running 3
done 1
running 4
done 4
running 5
done 0
done 3
done 5

method stable

method stable(Supply:D: $time:$scheduler = $*SCHEDULER --> Supply:D)

Creates a new supply that only passes on a value flowing through the given supply if it wasn't superseded by another value in the given $time (in seconds). Optionally uses another scheduler than the default scheduler, using the :scheduler parameter.

To clarify the above, if, during the timeout $time, additional values are emitted to the Supplier all but the last one will be thrown away. Each time an additional value is emitted to the Supplier, during the timeout, $time is reset.

This method can be quite useful when handling UI input, where it is not desired to perform an operation until the user has stopped typing for a while rather than on every keystroke.

my $supplier =;
my $supply1 = $supplier.Supply;
$supply1.tap(-> $v { say "Supply1 got: $v" });
my Supply $supply2 = $supply1.stable(5);
$supply2.tap(-> $v { say "Supply2 got: $v" });
$supplier.emit(43);  # will not be seen by $supply2 but will reset $time 
# OUTPUT: «Supply1 got: 42␤Supply1 got: 43␤Supply1 got: 44␤Supply2 got: 44␤» 

As can be seen above, $supply1 received all values emitted to the Supplier while $supply2 only received one value. The 43 was thrown away because it was followed by another 'last' value 44 which was retained and sent to $supply2 after approximately eight seconds, this due to the fact that the timeout $time was reset after three seconds.

method reduce

method reduce(Supply:D: &with --> Supply:D)

Creates a "reducing" supply with the same semantics as List.reduce.

my $supply = Supply.from-list(1..5).reduce({$^a + $^b});
$supply.tap(-> $v { say "$v" }); # OUTPUT: «15␤» 

method produce

method produce(Supply:D: &with --> Supply:D)

Creates a "producing" supply with the same semantics as List.produce.

my $supply = Supply.from-list(1..5).produce({$^a + $^b});
$supply.tap(-> $v { say "$v" }); # OUTPUT: «1␤3␤6␤10␤15␤» 

method lines

method lines(Supply:D: :$chomp = True --> Supply:D)

Creates a supply that will emit the characters coming in line by line from a supply that's usually created by some asynchronous I/O operation. The optional :chomp parameter indicates whether to remove line separators: the default is True.

method words

method words(Supply:D: --> Supply:D)

Creates a supply that will emit the characters coming in word for word from a supply that's usually created by some asynchronous I/O operation.

my $s = Supply.from-list("Hello Word!".comb);
my $ws = $s.words;
$ws.tap(&say);           # OUTPUT: «Hello␤Word!␤» 

method unique

method unique(Supply:D: :$as:$with:$expires --> Supply:D)

Creates a supply that only provides unique values, as defined by the optional :as and :with parameters (same as with List.unique). The optional :expires parameter how long to wait (in seconds) before "resetting" and not considering a value to have been seen, even if it's the same as an old value.

method squish

method squish(Supply:D: :$as:$with --> Supply:D)

Creates a supply that only provides unique values, as defined by the optional :as and :with parameters (same as with List.squish).

method max

method max(Supply:D: &custom-routine-to-use = &infix:<cmp> --> Supply:D)

Creates a supply that only emits values from the given supply if they are larger than any value seen before. In other words, from a continuously ascending supply it will emit all the values. From a continuously descending supply it will only emit the first value. The optional parameter specifies the comparator, just as with Any.max.

method min

method min(Supply:D: &custom-routine-to-use = &infix:<cmp> --> Supply:D)

Creates a supply that only emits values from the given supply if they are smaller than any value seen before. In other words, from a continuously descending supply it will emit all the values. From a continuously ascending supply it will only emit the first value. The optional parameter specifies the comparator, just as with Any.min.

method minmax

method minmax(Supply:D: &custom-routine-to-use = &infix:<cmp> --> Supply:D)

Creates a supply that emits a Range every time a new minimum or maximum values is seen from the given supply. The optional parameter specifies the comparator, just as with Any.minmax.

method skip

method skip(Supply:D: Int(Cool$number = 1 --> Supply:D)

Returns a new Supply which will emit all values from the given Supply except for the first $number values, which will be thrown away.

my $supplier =;
my $supply = $supplier.Supply;
$supply = $supply.skip(3);
$supply.tap({ say $_ });
$supplier.emit($_for 1..10# OUTPUT: «4␤5␤6␤7␤8␤9␤10␤» 

method start

method start(Supply:D: &startee --> Supply:D)

Creates a supply of supplies. For each value in the original supply, the code object is scheduled on another thread, and returns a supply either of a single value (if the code succeeds), or one that quits without a value (if the code fails).

This is useful for asynchronously starting work that you don't block on.

Use migrate to join the values into a single supply again.

method migrate

method migrate(Supply:D: --> Supply:D)

Takes a Supply which itself has values that are of type Supply as input. Each time the outer Supply emits a new Supply, this will be tapped and its values emitted. Any previously tapped Supply will be closed. This is useful for migrating between different data sources, and only paying attention to the latest one.

For example, imagine an application where the user can switch between different stocks. When they switch to a new one, a connection is established to a web socket to get the latest values, and any previous connection should be closed. Each stream of values coming over the web socket would be represented as a Supply, which themselves are emitted into a Supply of latest data sources to watch. The migrate method could be used to flatten this supply of supplies into a single Supply of the current values that the user cares about.

Here is a simple simulation of such a program:

my Supplier $stock-sources .= new;
sub watch-stock($symbol{
    $stock-sources.emit: supply {
        say "Starting to watch $symbol";
        whenever Supply.interval(1{
            emit "$symbol: 111." ~ 99.rand.Int;
        CLOSE say "Lost interest in $symbol";
$stock-sources.Supply.migrate.tap: *.say;
sleep 3;
sleep 3;

Which produces output like:

Starting to watch GOOG
GOOG: 111.67
GOOG: 111.20
GOOG: 111.37
Lost interest in GOOG
Starting to watch AAPL
AAPL: 111.55
AAPL: 111.6
AAPL: 111.6

Methods that combine supplies

method merge

method merge(Supply @*supplies --> Supply:D)

Creates a supply to which any value seen from the given supplies, is emitted. The resulting supply is done Only when all given supplies are done. Can also be called as a class method.

method zip

method zip(Supply @*supplies:&with = &[,] --> Supply:D)

Creates a supply that emits combined values as soon as there is a new value seen on all of the supplies. By default, Lists are created, but this can be changed by specifying your own combiner with the :with parameter. The resulting supply is done as soon as any of the given supplies are done. Can also be called as a class method.

method zip-latest

method zip-latest(Supply @*supplies:&with = &[,], :$initial --> Supply:D)

Creates a supply that emits combined values as soon as there is a new value seen on any of the supplies. By default, Lists are created, but this can be changed by specifying your own combiner with the :with parameter. The optional :initial parameter can be used to indicate the initial state of the combined values. By default, all supplies have to have at least one value emitted on them before the first combined values is emitted on the resulting supply. The resulting supply is done as soon as any of the given supplies are done. Can also be called as a class method.

I/O features exposed as supplies

sub signal

sub signal(*@signals:$scheduler = $*SCHEDULER)

Creates a supply for the Signal enums (such as SIGINT) specified, and an optional :scheduler parameter. Any signals received, will be emitted on the supply. For example:

signal(SIGINT).tap{ say "Thank you for your attention"exit 0 } );

would catch Control-C, thank you, and then exit.

To go from a signal number to a Signal, you can do something like this:

signal(Signal(2)).tap-> $sig { say "Received signal: $sig" } );

The list of supported signals can be found by checking Signal::.keys (as you would any enum). For more details on how enums work see enum.

Note: Currently Rakudo has a bug which makes it use numeric values of signals that may be incorrect for a particular system. For example, Signal(10) may return SIGBUS even if it is actually SIGUSR1 on your system. RT #132012


method watch-path($path --> Supply:D)

Creates a supply to which the OS will emit values to indicate changes on the file system for the given path. Also has a shortcut with the watch method on an IO object, like this:".").act{ say "$^file changed" } );
"."                     { say "$^file changed" } );   # same 

Type Graph

Type relations for Supply
perl6-type-graph Supply Supply Any Any Supply->Any Mu Mu Any->Mu

Stand-alone image: vector

Routines supplied by class Any

Supply inherits from class Any, which provides the following methods:

(Any) method ACCEPTS

Defined as:

multi method ACCEPTS(Any:D: Mu $other)



Returns True if $other === self (i.e. it checks object identity).

Many built-in types override this for more specific comparisons

(Any) method any

Defined as:

method any(--> Junction:D)

Interprets the invocant as a list and creates an any-Junction from it.

say so 2 == <1 2 3>.any;        # OUTPUT: «True␤» 
say so 5 == <1 2 3>.any;        # OUTPUT: «False␤» 

(Any) method all

Defined as:

method all(--> Junction:D)

Interprets the invocant as a list and creates an all-Junction from it.

say so 1 < <2 3 4>.all;         # OUTPUT: «True␤» 
say so 3 < <2 3 4>.all;         # OUTPUT: «False␤» 

(Any) method one

Defined as:

method one(--> Junction:D)

Interprets the invocant as a list and creates a one-Junction from it.

say so 1 == (123).one;      # OUTPUT: «True␤» 
say so 1 == (121).one;      # OUTPUT: «False␤» 

(Any) method none

Defined as:

method none(--> Junction:D)

Interprets the invocant as a list and creates a none-Junction from it.

say so 1 == (123).none;     # OUTPUT: «False␤» 
say so 4 == (123).none;     # OUTPUT: «True␤» 

(Any) method list

Defined as:

multi method list(Any:U: -->List)
multi method list(Any:D \SELF: -->List)

Applies the infix , operator to the invocant and returns the resulting List:

say 42.list.^name;           # OUTPUT: «List␤» 
say 42.list.elems;           # OUTPUT: «1␤» 

(Any) method push

Defined as:

method push(|values --> Positional:D)

The method push is defined for undefined invocants and allows for autovivifying undefined to an empty Array, unless the undefined value implements Positional already. The argument provided will then be pushed into the newly created Array.

my %h;
say %h<a>;     # OUTPUT: «(Any)␤»      <-- Undefined 
%h<a>.push(1); # .push on Any 
say %h;        # OUTPUT: «{a => [1]}␤» <-- Note the Array 

(Any) routine reverse

Defined as:

multi sub    reverse(*@list  --> Seq:D)
multi method reverse(List:D: --> Seq:D)

Returns a Seq with the same elements in reverse order.

Note that reverse always refers to reversing elements of a list; to reverse the characters in a string, use flip.


say <hello world!>.reverse;     # OUTPUT: «(world! hello)␤» 
say reverse ^10;                # OUTPUT: «(9 8 7 6 5 4 3 2 1 0)␤» 

(Any) method sort

Defined as:

multi method sort()
multi method sort(&custom-routine-to-use)

Sorts iterables with cmp or given code object and returns a new Seq. Optionally, takes a Callable as a positional parameter, specifying how to sort.


say <b c a>.sort;                           # OUTPUT: «(a b c)␤» 
say 'bca'.comb.sort.join;                   # OUTPUT: «abc␤» 
say 'bca'.comb.sort({$^b cmp $^a}).join;    # OUTPUT: «cba␤» 
say '231'.comb.sort(&infix:«<=>»).join;     # OUTPUT: «123␤» 

(Any) method map

Defined as:

multi method map(\SELF: &block;; :$label:$item)

map will iterate over the invocant and apply the number of positional parameters of the code object from the invocant per call. The returned values of the code object will become elements of the returned Seq.

The :$label and :$item are useful only internally, since for loops get converted to maps. The :$label takes an existing Label to label the .map's loop with and :$item controls whether the iteration will occur over (SELF,) (if :$item is set) or SELF.

(Any) method deepmap

Defined as:

method deepmap(&block --> Listis nodal

deepmap will apply &block to each element and return a new List with the return values of &block, unless the element does the Iterable role. For those elements deepmap will descend recursively into the sublist.

say [[1,2,3],[[4,5],6,7]].deepmap(* + 1);
# OUTPUT: «[[2 3 4] [[5 6] 7 8]]␤» 

(Any) method duckmap

Defined as:

method duckmap(&blockis rw is nodal

duckmap will apply &block on each element and return a new list with defined return values of the block. For undefined return values, duckmap will try to descend into the element if that element implements Iterable.

<a b c d e f g>.duckmap(-> $_ where <c d e>.any { .uc }).say;
# OUTPUT: «(a b C D E f g)␤» 
(('d''e'), 'f').duckmap(-> $_ where <e f>.any { .uc }).say;
# OUTPUT: «((d E) F)␤» 

(Any) method nodemap

Defined as:

method nodemap(&block --> Listis nodal

nodemap will apply &block to each element and return a new List with the return values of &block. In contrast to deepmap it will not descend recursively into sublists if it finds elements which does the Iterable role.

say [[1,2,3], [[4,5],6,7], 7].nodemap(*+1);
# OUTPUT: «(4, 4, 8)␤» 
say [[23], [4, [56]]]».nodemap(*+1)
# OUTPUT: «((3 4) (5 3))␤» 

The examples above would have produced the exact same results if we had used map instead of nodemap. The difference between the two lies in the fact that map flattens out slips while nodemap doesn't.

say [[2,3], [[4,5],6,7], 7].nodemap({.elems == 1 ?? $_ !! slip});
# OUTPUT: «(() () 7)␤» 
say [[2,3], [[4,5],6,7], 7].map({.elems == 1 ?? $_ !! slip});
# OUTPUT: «(7)␤» 

(Any) method flat

Defined as:

method flat(--> Seq:Dis nodal

Interprets the invocant as a list, flattens non-containerized Iterables into a flat list, and returns that list. Keep in mind Map and Hash types are Iterable and so will be flattened into lists of pairs.

say ((12), (3), %(:42a));      # OUTPUT: «((1 2) 3 {a => 42})␤» 
say ((12), (3), %(:42a)).flat# OUTPUT: «(1 2 3 a => 42)␤» 

Note that Arrays containerize their elements by default, and so flat will not flatten them. You can use hyper method call to call .List method on all the inner Iterables and so de-containerize them, so that flat can flatten them:

say [[123], [(45), 67]]      .flat# OUTPUT: «([1 2 3] [(4 5) 6 7])␤» 
say [[123], [(45), 67]]».List.flat# OUTPUT: «(1 2 3 4 5 6 7)␤» 

For more fine-tuned options, see deepmap, duckmap, and signature destructuring

(Any) method eager

Defined as:

method eager(--> Seq:Dis nodal

Interprets the invocant as a List, evaluates it eagerly, and returns that List.

my  $range = 1..5;
say $range;         # OUTPUT: «1..5␤» 
say $range.eager;   # OUTPUT: «(1 2 3 4 5)␤» 

(Any) method elems

Defined as:

method elems(--> Int:Dis nodal

Interprets the invocant as a list, and returns the number of elements in the list.

say 42.elems;                   # OUTPUT: «1␤» 
say <a b c>.elems;              # OUTPUT: «3␤» 

(Any) method end

method end(--> Any:Dis nodal

Interprets the invocant as a list, and returns the last index of that list.

say 6.end;                      # OUTPUT: «0␤» 
say <a b c>.end;                # OUTPUT: «2␤» 

(Any) method pairup

Defined as:

method pairup(--> Seq:Dis nodal

Interprets the invocant as a list, and constructs a list of pairs from it, in the same way that assignment to a Hash does. That is, it takes two consecutive elements and constructs a pair from them, unless the item in the key position already is a pair (in which case the pair is passed through, and the next list item, if any, is considered to be a key again).

say (=> 1'b''c').pairup.perl;     # OUTPUT: «(:a(1), :b("c")).Seq␤» 

(Any) sub exit

Defined as:

sub exit(Int() $status = 0)

Exits the current process with return code $status or zero if no value has been specified. The exit value ($status), when different from zero, has to be opportunely evaluated from the process that catches it (e.g., a shell).

exit does prevent the LEAVE phaser to be executed.

exit should be used as last resort only to signal the parent process about an exit code different from zero, and should not be used to terminate exceptionally a method or a sub: use exceptions instead.

It is worth noting that the only way to return an exit code different from zero from a Main function is by means of using exit.

(Any) sub item

Defined as:

proto sub item(|) is pure
multi item(\x)
multi item(|c)
multi item(Mu $a)

Forces given object to be evaluated in item context and returns the value of it.

say item([1,2,3]).perl;              # OUTPUT: «$[1, 2, 3]␤» 
say item( %apple => 10 ) ).perl;   # OUTPUT: «${:apple(10)}␤» 
say item("abc").perl;                # OUTPUT: «"abc"␤» 

You can also use $ as item contextualizer.

say $[1,2,3].perl;                   # OUTPUT: «$[1, 2, 3]␤» 
say $("abc").perl;                   # OUTPUT: «"abc"␤» 

(Any) method Array

Defined as:

method Array(--> Array:Dis nodal

Coerce the invocant to Array.

(Any) method List

Defined as:

method List(--> List:Dis nodal

Coerce the invocant to List, using the list method.

(Any) method Hash

Defined as:

proto method Hash(|) is nodal
multi method Hash--> Hash:D)

Coerce the invocant to Hash by invoking the method hash on it.

(Any) method hash

Defined as:

proto method hash(|) is nodal
multi method hash(Any:U: --> Hash:D)
multi method hash(Any:D: --> Hash:D)

Creates a new Hash, empty in the case the invocant is undefined, or coerces the invocant to an Hash in the case it is defined.

my $d# $d is Any 
say $d.hash# OUTPUT: {} 
$d.append: 'a''b';
say $d.hash# OUTPUT: {a => b} 

(Any) method Slip

Defined as:

method Slip(--> Slip:Dis nodal

Coerce the invocant to Slip.

(Any) method Map

Defined as:

method Map(--> Map:Dis nodal

Coerce the invocant to Map.

(Any) method Bag

Defined as:

method Bag(--> Bag:Dis nodal

Coerce the invocant to Bag, whereby Positionals are treated as lists of values.

(Any) method BagHash

Defined as:

method BagHash(--> BagHash:Dis nodal

Coerce the invocant to BagHash, whereby Positionals are treated as lists of values.

(Any) method Set

Defined as:

method Set(--> Set:Dis nodal

Coerce the invocant to Set, whereby Positionals are treated as lists of values.

(Any) method SetHash

Defined as:

method SetHash(--> SetHash:Dis nodal

Coerce the invocant to SetHash, whereby Positionals are treated as lists of values.

(Any) method Mix

Defined as:

method Mix(--> Mix:Dis nodal

Coerce the invocant to Mix, whereby Positionals are treated as lists of values.

(Any) method MixHash

Defined as:

method MixHash(--> MixHash:Dis nodal

Coerce the invocant to MixHash, whereby Positionals are treated as lists of values.

(Any) method Supply

Defined as:

method Supply(--> Supply:Dis nodal

Coerce the invocant first to a list by applying the invocant's .list method, and then to a Supply.

(Any) method min

Defined As:

multi method min(--> Any:D)
multi method min(&filter --> Any:D)

Coerces to Iterable and returns the numerically smallest element.

If a Callable positional argument is provided, each value is passed into the filter, and its return value is compared instead of the original value. The original value is still the one returned from min.

say (1,7,3).min();       # OUTPUT:«1␤» 
say (1,7,3).min({1/$_}); # OUTPUT:«7␤» 

(Any) method max

Defined As:

multi method max(--> Any:D)
multi method max(&filter --> Any:D)

Coerces to Iterable and returns the numerically largest element.

If a Callable positional argument is provided, each value is passed into the filter, and its return value is compared instead of the original value. The original value is still the one returned from max.

say (1,7,3).max();       # OUTPUT:«7␤» 
say (1,7,3).max({1/$_}); # OUTPUT:«1␤» 

(Any) method minmax

Defined As:

multi method minmax(--> Range:D)
multi method minmax(&filter --> Range:D)

Returns a Range from the smallest to the largest element.

If a Callable positional argument is provided, each value is passed into the filter, and its return value is compared instead of the original value. The original values are still used in the returned Range.

say (1,7,3).minmax();      # OUTPUT:«1..7␤» 
say (1,7,3).minmax({-$_}); # OUTPUT:«7..1␤» 

(Any) method minpairs

Defined As:

multi method minpairs(Any:D: --> Seq:D)

Calls .pairs and returns a Seq with all of the Pairs with minimum values, as judged by the cmp operator:

<a b c a b c>.minpairs.perl.put# OUTPUT: «(0 => "a", 3 => "a").Seq␤» 
%(:42a, :75b).minpairs.perl.put# OUTPUT: «(:a(42),).Seq␤» 

(Any) method maxpairs

Defined As:

multi method maxpairs(Any:D: --> Seq:D)

Calls .pairs and returns a Seq with all of the Pairs with maximum values, as judged by the cmp operator:

<a b c a b c>.maxpairs.perl.put# OUTPUT: «(2 => "c", 5 => "c").Seq␤» 
%(:42a, :75b).maxpairs.perl.put# OUTPUT: «(:b(75),).Seq␤» 

(Any) method keys

Defined As:

multi method keys(Any:U: --> List)
multi method keys(Any:D: --> List)

For defined Any returns its keys after calling list on it, otherwise calls list and returns it.

say Any.keys# OUTPUT: «()␤» 

(Any) method flatmap

Defined As:

method flatmap(Any:U: &code --> Seq)

Coerces the Any to a list by applying the .list method and uses List.flatmap on it.

say Any.flatmap({.reverse}); # OUTPUT: «((Any))␤» 

In the case of Any, Any.list returns a 1-item list, as is shown.

(Any) method roll

Defined As:

multi method roll(--> Any)
multi method roll($n --> Seq)

Coerces the invocant Any to a list by applying the .list method and uses List.roll on it.

say Any.roll;    # OUTPUT: «(Any)␤» 
say Any.roll(5); # OUTPUT: «((Any) (Any) (Any) (Any) (Any))␤» 

(Any) method pick

Defined As:

multi method pick(--> Any)
multi method pick($n --> Seq)

Coerces the Any to a list by applying the .list method and uses List.pick on it.

say Any.pick;    # OUTPUT: «(Any)␤» 
say Any.pick(5); # OUTPUT: «((Any))␤» 

(Any) method skip

Defined As:

multi method skip(--> Seq)
multi method skip($n --> Seq)

Creates a Seq from 1-item list's iterator and uses Seq.skip on it.

say Any.skip;      # OUTPUT: «()␤» 
say Any.skip(5);   # OUTPUT: «()␤» 
say Any.skip(-1);  # OUTPUT: «((Any))␤» 
say Any.skip(*-1); # OUTPUT: «((Any))␤» 

(Any) method prepend

Defined As:

multi method prepend(--> Array)
multi method prepend(@values --> Array)

Initializes Any variable as empty Array and calls Array.prepend on it.

my $a;
say $a.prepend# OUTPUT: «[]␤» 
say $a;         # OUTPUT: «[]␤» 
my $b;
say $b.prepend(1,2,3); # OUTPUT: «[1 2 3]␤» 

(Any) method unshift

Defined As:

multi method unshift(--> Array)
multi method unshift(@values --> Array)

Initializes Any variable as empty Array and calls Array.unshift on it.

my $a;
say $a.unshift# OUTPUT: «[]␤» 
say $a;         # OUTPUT: «[]␤» 
my $b;
say $b.unshift([1,2,3]); # OUTPUT: «[[1 2 3]]␤» 

(Any) method first

Defined As:

method first(Mu $matcher?:$k:$kv:$p:$end)

Treats the Any as a 1-item list and uses List.first on it.

say Any.first# OUTPUT: «(Any)␤» 

(Any) method unique

Defined As:

method unique(:&as:&with --> Seq:D)

Treats the Any as a 1-item list and uses List.unique on it.

say Any.unique# OUTPUT: «((Any))␤» 

(Any) method repeated

Defined As:

method repeated(:&as:&with --> Seq)

Treats the Any as a 1-item list and uses List.repeated on it.

say Any.repeated# OUTPUT: «()␤» 

(Any) method squish

Defined As:

method squish(:&as:&with --> Seq)

Treats the Any as a 1-item list and uses List.squish on it.

say Any.squish# OUTPUT: «((Any))␤» 

(Any) method permutations

Defined As:

method permutations(--> Seq)

Treats the Any as a 1-item list and uses List.permutations on it.

say Any.permutations# OUTPUT: «(((Any)))␤» 

(Any) method categorize

Defined As:

method categorize(&mapper --> Hash:D)

Treats the Any as a 1-item list and uses List.categorize on it.

say Any.categorize({ $_ }); # OUTPUT: «{(Any) => [(Any)]}␤» 

(Any) method classify

Defined As:

method classify(&mapper -->Hash:D)

Treats the Any as a 1-item list and uses List.classify on it.

say Any.classify({ $_ }); # OUTPUT: «{(Any) => [(Any)]}␤» 

(Any) method produce

(Any) method pairs

Defined As:

multi method pairs(Any:U:  -->List)
multi method pairs(Any:D:  -->List)

Returns an empty List if the invocant is undefined, otherwise converts the invocant to a List via the list method and calls List.pairs on it:

say Any.pairs# OUTPUT: «()␤» 
my $a;
say $a.pairs;  # OUTPUT: «()» 
$a =;
say $a.pairs;  # OUTPUT: «(0 =>» 

(Any) method antipairs

Defined As:

multi method antipairs(Any:U:  -->List)
multi method antipairs(Any:D:  -->List)

Applies the method List.antipairs to the invocant, if it is defined, after having invoked list on it. If the invocant is not defined, it returns an empty List:

my $a;
say $a.antipairs;      # OUTPUT: «()» 
$a =;
say $a.antipairs;      # OUTPUT: «( => 0)» 

(Any) method kv

Defined As:

multi method kv(Any:U:  -->List)
multi method kv(Any:D:  -->List)

Returns an empty List if the invocant is not defined, otherwise it does invoke list on the invocant and then returns the result of List.kv on the latter:

my $a;
say $a.kv;      # OUTPUT: «()» 
$a =;
say $a.kv;      # OUTPUT: «(0» 
say Any.kv;     # OUTPUT: «()␤» 

(Any) method toggle

Defined as:

method toggle(Any:D: *@conditions where .all ~~ Callable:DBool :$off  --> Seq:D)

Iterates over the invocant, producing a Seq, toggling whether the received values are propagated to the result on and off, depending on the results of calling Callables in @conditions:

say ^10 .toggle: * < 4* %% 2&is-prime# OUTPUT: «(0 1 2 3 6 7)␤» 
say ^10 .toggle: :off* > 4;              # OUTPUT: «(5 6 7 8 9)␤» 

Imagine a switch that's either on or off (True or False), and values are produced if it's on. By default, the initial state of that switch is in "on" position, unless :$off is set to a true value, in which case the initial state will be "off".

A Callable from the head of @conditions is taken (if any are available) and it becomes the current tester. Each value from the original sequence is tested by calling the tester Callable with that value. The state of our imaginary switch is set to the return value from the tester: if it's truthy, set switch to "on", otherwise set it to "off".

Whenever the switch is toggled (i.e. switched from "off" to "on" or from "on" to "off"), the current tester Callable is replaced by the next Callable in @conditions, if available, which will be used to test any further values. If no more tester Callables are available, the switch will remain in its current state until the end of iteration.

# our original sequence of elements: 
say list ^10# OUTPUT: «(0 1 2 3 4 5 6 7 8 9)␤» 
# toggled result: 
say ^10 .toggle: * < 4* %% 2&is-prime# OUTPUT: «(0 1 2 3 6 7)␤» 
# First tester Callable is `* < 4` and initial state of switch is "on". 
# As we iterate over our original sequence: 
# 0 => 0 < 4 === True  switch is on, value gets into result, switch is 
#                      toggled, so we keep using the same Callable: 
# 1 => 1 < 4 === True  same 
# 2 => 2 < 4 === True  same 
# 3 => 3 < 4 === True  same 
# 4 => 4 < 4 === False switch is now off, "4" does not make it into the 
#                      result. In addition, our switch got toggled, so 
#                      we're switching to the next tester Callable 
# 5 => 5 %% 2 === False  switch is still off, keep trying to find a value 
# 6 => 6 %% 2 === True   switch is now on, take "6" into result. The switch 
#                        toggled, so we'll use the next tester Callable 
# 7 => is-prime(7) === True  switch is still on, take value and keep going 
# 8 => is-prime(8) === False switch is now off, "8" does not make it into 
#                            the result. The switch got toggled, but we 
#                            don't have any more tester Callables, so it 
#                            will remain off for the rest of the sequence. 

Since the toggle of the switch's state loads the next tester Callable, setting :$off to a True value affects when first tester is discarded:

# our original sequence of elements: 
say <0 1 2># OUTPUT: «(0 1 2)␤» 
# toggled result: 
say <0 1 2>.toggle: * > 1# OUTPUT: «()␤» 
# First tester Callable is `* > 1` and initial state of switch is "on". 
# As we iterate over our original sequence: 
# 0 => 0 > 1 === False  switch is off, "0" does not make it into result. 
#                      In addition, switch got toggled, so we change the 
#                      tester Callable, and since we don't have any more 
#                      of them, the switch will remain "off" until the end 
# our original sequence of elements: 
say <0 1 2># OUTPUT: «(0 1 2)␤» 
# toggled result: 
say <0 1 2>.toggle: :off* > 1# OUTPUT: «(2)␤» 
# First tester Callable is `* > 1` and initial state of switch is "off". 
# As we iterate over our original sequence: 
# 0 => 0 > 1 === False  switch is off, "0" does not make it into result. 
#                       The switch did NOT get toggled this time, so we 
#                       keep using our current tester Callable 
# 1 => 1 > 1 === False  same 
# 2 => 2 > 1 === True   switch is on, "2" makes it into the result 

(Any) method tree

Defined As:

method tree(--> Any)

Returns the class if it's undefined or if it's not iterable, returns the result of applying the tree method to the elements if it's Iterable.

say Any.tree# OUTPUT: «Any␤» 

.tree has different prototypes for Iterable elements.

my @floors = ( 'A', ('B','C', ('E','F','G')));
say @floors.tree(1).flat.elems# OUTPUT: «6␤» 
say @floors.tree(2).flat.elems# OUTPUT: «2␤» 
say @floors.tree*.join("-"), *.join(""), *.join("|" )); # OUTPUT: «A-B—C—E|F|G␤» 

With a number, it iteratively applies tree to every element in the lower level; the first instance will apply .tree(0) to every element in the array, and likewise for the next example.

The second prototype applies the Whatever code passed as arguments to every level in turn; the first argument will go to level 1 and so on. tree can, thus, be a great way to process complex all levels of complex, multi-level, data structures.

(Any) method nl-out

Defined As:

method nl-out(--> Str)

Returns Str with the value of "\n". See for the details.

say OUTPUT: «␤␤» 

(Any) method invert

Defined As:

method invert(--> List)

Returns an empty List.

say Any.invert# OUTPUT: «()␤» 

(Any) method combinations

Defined As:

method combinations(--> Seq)

Treats the Any as a 1-item list and uses List.combinations on it.

say Any.combinations# OUTPUT: «(() ((Any)))␤» 

(Any) method iterator

Defined As:

method iterator(--> Iterator)

Coerces the Any to a list by applying the .list method and uses iterator on it.

my $it = Any.iterator;
say $it.pull-one# OUTPUT: «(Any)␤» 
say $it.pull-one# OUTPUT: «IterationEnd␤» 

(Any) method grep

Defined As:

method grep(Mu $matcher:$k:$kv:$p:$v --> Seq)

Coerces the Any to a list by applying the .list method and uses List.grep on it.

Based on $matcher value can be either ((Any)) or empty List.

my $a;
say $a.grep({ True }); # OUTPUT: «((Any))␤» 
say $a.grep({ $_ });   # OUTPUT: «()␤» 

(Any) method append

Defined As:

proto method append(|) is nodal {*}
multi method append(Any:U \SELF: |values --> Array)

In the case the instance is not a positional-thing, it instantiate it as a new Array, otherwise clone the current instance. After that, it appends the values passed as arguments to the array obtained calling Array.append on it.

my $a;
say $a.append# OUTPUT: «[]␤» 
my $b;
say $b.append((1,2,3)); # OUTPUT: «[1 2 3]␤» 

(Any) method values

Defined As:

method values(--> List)

Returns an empty List.

(Any) method collate

Defined As:

method collate(--> Seq)


(Any) method cache

Defined As:

method cache(--> List)

Provides a List representation of the object itself, calling the method list on the instance.

Routines supplied by class Mu

Supply inherits from class Mu, which provides the following methods:

(Mu) method defined

Declared as

multi method defined(   --> Bool:D)

Returns False on the type object, and True otherwise.

say Int.defined;                # OUTPUT: «False␤» 
say 42.defined;                 # OUTPUT: «True␤» 

Very few types (like Failure) override defined to return False even for instances:

sub fails() { fail 'oh noe' };
say fails().defined;            # OUTPUT: «False␤» 

(Mu) routine defined

Declared as

multi sub    defined(Mu --> Bool:D)

invokes the .defined method on the object and returns its result.

(Mu) routine isa

multi method isa(Mu $type     --> Bool:D)
multi method isa(Str:D $type  --> Bool:D)

Returns True if the invocant is an instance of class $type, a subset type or a derived class (through inheritance) of $type.

my $i = 17;
say $i.isa("Int");   # OUTPUT: «True␤» 
say $i.isa(Any);     # OUTPUT: «True␤» 

A more idiomatic way to do this is to use the smartmatch operator ~~ instead.

my $s = "String";
say $s ~~ Str;       # OUTPUT: «True␤» 

(Mu) routine does

method does(Mu $type --> Bool:D)

Returns True if and only if the invocant conforms to type $type.

my $d ='2016-06-03');
say $d.does(Dateish);             # True    (Date does role Dateish) 
say $d.does(Any);                 # True    (Date is a subclass of Any) 
say $d.does(DateTime);            # False   (Date is not a subclass of DateTime) 

Using the smart match operator ~~ is a more idiomatic alternative.

my $d ='2016-06-03');
say $d ~~ Dateish;                # OUTPUT: «True␤» 
say $d ~~ Any;                    # OUTPUT: «True␤» 
say $d ~~ DateTime;               # OUTPUT: «False␤» 

(Mu) routine Bool

multi sub    Bool(Mu --> Bool:D)
multi method Bool(   --> Bool:D)

Returns False on the type object, and True otherwise.

Many built-in types override this to be False for empty collections, the empty string or numerical zeros

say Mu.Bool;                    # OUTPUT: «False␤» 
say;                # OUTPUT: «True␤» 
say [123].Bool;             # OUTPUT: «True␤» 
say [].Bool;                    # OUTPUT: «False␤» 
say %hash => 'full' ).Bool;   # OUTPUT: «True␤» 
say {}.Bool;                    # OUTPUT: «False␤» 
say "".Bool;                    # OUTPUT: «False␤» 
say 0.Bool;                     # OUTPUT: «False␤» 
say 1.Bool;                     # OUTPUT: «True␤» 
say "0".Bool;                   # OUTPUT: «True␤» 

(Mu) method Capture

Declared as:

method Capture(Mu:D: --> Capture:D)

Returns a Capture with named arguments corresponding to invocant's public attributes:

class Foo {
    has $.foo = 42;
    has $.bar = 70;
    method bar { 'something else' }
}.new.Capture.say# OUTPUT: «\(:bar("something else"), :foo(42))␤» 

(Mu) method Str

multi method Str(--> Str)

Returns a string representation of the invocant, intended to be machine readable. Method Str warns on type objects, and produces the empty string.

say Mu.Str;                     # Use of uninitialized value of type Mu in string context. 

(Mu) routine gist

multi sub    gist(+args --> Str)
multi method gist(   --> Str)

Returns a string representation of the invocant, optimized for fast recognition by humans. As such lists will be truncated at 100 elements. Use .perl to get all elements.

The default gist method in Mu re-dispatches to the perl method for defined invocants, and returns the type name in parenthesis for type object invocants. Many built-in classes override the case of instances to something more specific that may truncate output.

gist is the method that say calls implicitly, so say $something and say $something.gist generally produce the same output.

say Mu.gist;        # OUTPUT: «(Mu)␤» 
say;    # OUTPUT: «␤» 

(Mu) routine perl

multi method perl(--> Str)

Returns a Perlish representation of the object (i.e., can usually be re-evaluated with EVAL to regenerate the object). The exact output of perl is implementation specific, since there are generally many ways to write a Perl expression that produces a particular value

(Mu) method item

method item(Mu \item:is raw

Forces the invocant to be evaluated in item context and returns the value of it.

say [1,2,3].item.perl;          # OUTPUT: «$[1, 2, 3]␤» 
say %apple => 10 ).item.perl# OUTPUT: «${:apple(10)}␤» 
say "abc".item.perl;            # OUTPUT: «"abc"␤» 

(Mu) method self

method self(--> Mu)

Returns the object it is called on.

(Mu) method clone

method clone(*%twiddles)

Creates a shallow clone of the invocant, including shallow cloning of private attributes. Alternative values for public attributes can be provided via named arguments with names matching the attributes' names.

class Point2D {
    has ($.x$.y);
    multi method gist(Point2D:D:{
my $p = => 2=> 3);
say $p;                     # OUTPUT: «Point(2, 3)␤» 
say $p.clone(=> -5);      # OUTPUT: «Point(2, -5)␤» 

Note that .clone does not go the extra mile to shallow-copy @. and %. sigiled attributes and, if modified, the modifications will still be available in the original object:

class Foo {
    has $.foo is rw = 42;
    has &.boo is rw = { say "Hi" };
    has       = <a b>;
    has %.baz       = <a b c d>;
my $o1 =;
with my $o2 = $o1.clone {
    .foo = 70;
    .bar = <Z Y>;
    .baz = <Z Y X W>;
    .boo = { say "Bye" };
# Hash and Array attribute modifications in clone appear in original as well: 
say $o1;    # OUTPUT: « => 42, bar => ["Z", "Y"], baz => {:X("W"), :Z("Y")}, …␤» 
say $o2;    # OUTPUT: « => 70, bar => ["Z", "Y"], baz => {:X("W"), :Z("Y")}, …␤» 
$; # OUTPUT: «Hi␤» 
$; # OUTPUT: «Bye␤» 

To clone those, you could implement your own .clone that clones the appropriate attributes and passes the new values to Mu.clone, for example, via nextwith. Alternatively, your own .clone could clone self first (using self.Mu::clone or callsame) and then manipulate the clone as needed, before returning it.

class Bar {
    has = <a b>;
    has = <a b c d>;
    method clone { nextwith :foo(@!foo.clone:bar(%!bar.clone}
my $o1 =;
with my $o2 = $o1.clone {
    .foo = <Z Y>;
    .bar = <Z Y X W>;
# Hash and Array attribute modifications in clone do not affect original: 
say $o1# OUTPUT: « => ["a", "b"], bar => {:a("b"), :c("d")})␤» 
say $o2# OUTPUT: « => ["Z", "Y"], bar => {:X("W"), :Z("Y")})␤» 

(Mu) method new

multi method new(*%attrinit)

Default method for constructing (create + initialize) new objects of a class. This method expects only named arguments which are then used to initialize attributes with accessors of the same name.

Classes may provide their own new method to override this default.

new triggers an object construction mechanism that calls submethods named BUILD in each class of an inheritance hierarchy, if they exist. See the documentation on object construction for more information.

(Mu) method bless

method bless(*%attrinit --> Mu:D)

Lower-level object construction method than new.

Creates a new object of the same type as the invocant, uses the named arguments to initialize attributes, and returns the created object.

You can use this method when writing custom constructors:

class Point {
    has $.x;
    has $.y;
    multi method new($x$y{
my $p =;

(Though each time you write a custom constructor, remember that it makes subclassing harder).

(Mu) method CREATE

method CREATE(--> Mu:D)

Allocates a new object of the same type as the invocant, without initializing any attributes.

say Mu.CREATE.defined;  # OUTPUT: «True␤» 

(Mu) method print

multi method print(--> Bool:D)

Prints value to $*OUT after stringification using .Str method without adding a newline at end.

"abc\n".print;          # RESULT: «abc␤» 

(Mu) method put

multi method put(--> Bool:D)

Prints value to $*OUT, adding a newline at end, and if necessary, stringifying non-Str object using the .Str method.

"abc".put;              # RESULT: «abc␤» 

(Mu) method say

multi method say(--> Bool:D)

Prints value to $*OUT after stringification using gist method with newline at end. To produce machine readable output use .put.

say 42;                 # OUTPUT: «42␤» 

(Mu) method ACCEPTS

multi method ACCEPTS(Mu:U: $other)

ACCEPTS is the method that smart matching with the infix ~~ operator and given/when invokes on the right-hand side (the matcher).

The Mu:U multi performs a type check. Returns True if $other conforms to the invocant (which is always a type object or failure).

say 42 ~~ Mu;           # OUTPUT: «True␤» 
say 42 ~~ Int;          # OUTPUT: «True␤» 
say 42 ~~ Str;          # OUTPUT: «False␤» 

Note that there is no multi for defined invocants; this is to allow autothreading of junctions, which happens as a fallback mechanism when no direct candidate is available to dispatch to.

(Mu) method WHICH

multi method WHICH(--> ObjAt:D)

Returns an object of type ObjAt which uniquely identifies the object. Value types override this method which makes sure that two equivalent objects return the same return value from WHICH.

say 42.WHICH eq 42.WHICH;       # OUTPUT: «True␤» 

(Mu) method WHERE

method WHERE(--> Int)

Returns an Int representing the memory address of the object.

(Mu) method WHY

multi method WHY(--> Pod::Block::Declarator)

Returns the attached Pod::Block::Declarator.

For instance:

#| Initiate a specified spell normally 
sub cast(Spell $s{
#= (do not use for class 7 spells) 
say &cast.WHY;
# OUTPUT: «Initiate a specified spell normally␤(do not use for class 7 spells)␤» 

See Pod declarator blocks for details about attaching Pod to variables, classes, functions, methods, etc.

(Mu) trait is export

multi sub trait_mod:<is>(Mu:U \type:$export!)

Marks a type as being exported, that is, available to external users.

my class SomeClass is export { }

A user of a module or class automatically gets all the symbols imported that are marked as is export.

See Exporting and Selective Importing Modules for more details.

(Mu) method return

method return()

The method return will stop execution of a subroutine or method, run all relevant phasers and provide invocant as a return value to the caller. If a return type constraint is provided it will be checked unless the return value is Nil. A control exception is raised and can be caught with CONTROL.

sub f { (1|2|3).return };
say f(); # OUTPUT: «any(1, 2, 3)␤» 

(Mu) method return-rw

Same as method return except that return-rw returns a writable container to the invocant (see more details here: return-rw).

(Mu) method emit

method emit()

Emits the invocant into the enclosing supply or react block.

react { whenever supply { .emit for "foo"42.5 } {
    say "received {.^name} ($_)";
# received Str (foo) 
# received Int (42) 
# received Rat (0.5) 

(Mu) method take

method take()

Returns the invocant in the enclosing gather block.

sub insert($sep+@list{
    gather for @list {
        FIRST .takenext;
        take slip $sep.item
say insert ':', <a b c>;
# OUTPUT: «(a : b : c)␤» 

(Mu) routine take

sub take(\item)

Takes the given item and passes it to the enclosing gather block.

#| randomly select numbers for lotto 
my $num-selected-numbers = 6;
my $max-lotto-numbers = 49;
gather for ^$num-selected-numbers {
    take (1 .. $max-lotto-numbers).pick(1);
}.say;    # six random values 

(Mu) routine take-rw

sub take-rw(\item)

Returns the given item to the enclosing gather block, without introducing a new container.

my @a = 1...3;
sub f(@list){ gather for @list { take-rw $_ } };
for f(@a{ $_++ };
say @a;
# OUTPUT: «[2 3 4]␤» 

(Mu) method so

method so()

Returns a Bool value representing the logical non-negation of an expression. One can use this method similarly to the English sentence: "If that is so, then do this thing". For instance,

my @args = <-a -e -b -v>;
my $verbose-selected = any(@argseq '-v' | '-V';
if $ {
    say "Verbose option detected in arguments";
} # OUTPUT: «Verbose option detected in arguments␤» 

(Mu) method not

method not()

Returns a Bool value representing the logical negation of an expression. Thus it is the opposite of so.

my @args = <-a -e -b>;
my $verbose-selected = any(@argseq '-v' | '-V';
if $verbose-selected.not {
    say "Verbose option not present in arguments";
} # OUTPUT: «Verbose option not present in arguments␤» 

Since there is also a prefix version of not, the above code reads better like so:

my @args = <-a -e -b>;
my $verbose-selected = any(@argseq '-v' | '-V';
if not $verbose-selected {
    say "Verbose option not present in arguments";
} # OUTPUT: «Verbose option not present in arguments␤»