In RaceSeq§
See primary documentation in context for method map
method map(RaceSeq: , *)
Uses maps on the RaceSeq
, generally created by application of .race
to a preexisting Seq
.
In Supply§
See primary documentation in context for method map
method map(Supply: --> Supply)
Returns a new supply that maps each value of the given supply through &mapper
and emits it to the new supply.
my = Supplier.new;my = .Supply;my = .map(-> );.tap();.emit(4); # OUTPUT: «8»
In List§
See primary documentation in context for routine map
multi method map(\SELF: )multi map(, +values)
Examples applied to lists are included here for the purpose of illustration.
For a list, it invokes &code
for each element and gathers the return values in a sequence and returns it. This happens lazily, i.e. &code
is only invoked when the return values are accessed.Examples:
say ('hello', 1, 22/7, 42, 'world').map: # OUTPUT: «(Str Int Rat Int Str)»say map *.Str.chars, 'hello', 1, 22/7, 42, 'world'; # OUTPUT: «(5 1 8 2 5)»
map
inspects the arity of the code object, and tries to pass as many arguments to it as expected:
sub b(, ) ;say <a b x y>.map().join(', '); # OUTPUT: «a before b, x before y»
iterates the list two items at a time.
Note that map
does not flatten embedded lists and arrays, so
((1, 2), <a b>).map()
passes (1, 2)
and <a b>
in turn to the block, leading to a total of two iterations and the result sequence "1,2", "a,b"
.
If &code
is a Block
loop phasers will be executed and loop control statements will be treated as in loop control flow. Please note that return
is executed in the context of its definition. It is not the return statement of the block but the surrounding Routine. Using a Routine
will also handle loop control statements and loop phasers. Any Routine
specific control statement or phaser will be handled in the context of that Routine
.
sub s;s# OUTPUT: «hi»
In HyperSeq§
See primary documentation in context for method map
method map(HyperSeq: , *)
Uses maps on the HyperSeq
, generally created by application of hyper
to a preexisting Seq
.
In Any§
See primary documentation in context for routine map
multi method map(\SELF: )multi map(, +values)
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 map
s. 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
.
In sub
form, it will apply the code
block to the values
, which will be used as invocant.
The forms with |c
, Iterable:D \iterable
and Hash:D \hash
as signatures will fail with X::Cannot::Map
, and are mainly meant to catch common traps.
Inside a for
statement that has been sunk, a Seq
created by a map will also sink:
say gather for 1# OUTPUT: «(0 1 2)»
In this case, gather
sinks the for
statement, and the result of sinking the Seq
will be iterating over its elements, calling .take
on them.
In Backtrace§
See primary documentation in context for method map
multi method map(Backtrace: --> Seq)
It invokes &block
for each element and gathers the return values in a sequence and returns it.
This program:
sub innersub outerouter;
results in:
SETTING::src/core.c/Backtrace.rakumod: 85 SETTING::src/core.c/Backtrace.rakumod: 85 test.raku: 1 test.raku: 2 test.raku: 3 test.raku: 1