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Clarification on &done and &emit #4721

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Nov 26, 2025
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Clarification on &done and &emit #4721

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22 changes: 16 additions & 6 deletions doc/Type/independent-routines.rakudoc
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Original file line number Diff line number Diff line change
Expand Up @@ -1324,6 +1324,10 @@ my $supply = supply {
$supply.tap( -> $v { say "First : $v" });
=end code

C<emit> is implemented as a L<control exception|/language/phasers#CONTROL> and
can therefore be used by something called from the C<supply> block that it
refers to.

See also L<the page for C<emit> methods|/routine/emit>.

=head2 sub undefine
Expand Down Expand Up @@ -1459,24 +1463,30 @@ of any subsequent calls to C<exit> in the same, or any other thread.
sub done(--> Nil)

If used outside any supply or react block, throws an exception C<done without
supply or react>. Within a L<C<Supply>|/type/Supply> block, it will indicate the
supply will no longer emit anything. See also L<documentation on method
C<done>|/routine/done>.
supply or react>. Within a L<C<Supply>|/type/Supply> block, it will signal that
the supply will not emit further values, and leaves the supply block. See also
L<documentation on method C<done>|/routine/done>.

C<done> is implemented as a L<control exception|/language/phasers#CONTROL> and
can therefore be used by something called from the C<supply> or C<react> block
that it refers to.

=for code
my $supply = supply {
for 1 .. 3 {
emit($_);
}
done;
say "never reached";
}
$supply.tap( -> $v { say "Second : $v" }, done => { say "No more" });
# OUTPUT: «Second : 1␤Second : 2␤Second : 3␤No More␤»

The block passed to the C<done> named argument will be run when C<done> is
called within the C<supply> block.
The block passed to the C<done> named argument when tapping the supply will be
run when C<done> is called within the C<supply> block. Similarly, C<whenever>
blocks that were used to tap the supply will have any C<LAST> phasers called.

As of the 2021.06 release of the Rakudo compiler, it is also possibly to
As of the 2021.06 release of the Rakudo compiler, it is also possible to
supply a value with C<done>:

sub done($value --> Nil)
Expand Down