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Rake zef:lizmat last updated on 2021-09-08



Rake - raking typed values together in a list


use Rake;

my $foo = Rake[Int,Str,IO].new(42,"bar","filename".IO);
say $foo[0];  # id: 42
say $foo[1];  # name: bar
say $foo[2];  # path: "filename".IO

.say for $foo;  # 42␤bar␤"filename".IO␤

say $foo.^name;  # Rake[Int,Str,IO]

my @bar := Rake[Int,Int].new(42,666);

constant RIS = Rake[Int,Str];        # Rakudo < v2020.06
my @baz is RIS = 42,"foo";

my @baz is Rake[Int,Str] = 42,"foo"; # Rakudo >= v2020.06

class CIS does Rake[Int,Str] { }
my @caz is CIS = 42,"foo";

sub take-rake(Rake[Int,Str] $raked) {
    say "got: $raked";

sub answers(*@answers) {
    Rake[Int xx @answers, :value-type].new(@answers)
say (answers(42,666), answers(42,666)).Set.elems;  #1


The Rake class (actually, a punned role) allows one to create an ad-hoc collection of typed objects without the need to use a hash, list or class. It only accepts values that smartmatch the given types on creation of the collection and provides immutable positional values from the result.

It can be iterated over and be passed around as a single object. It can also be used as a constraint in dispatch.

Optionally, it can force objects of the Rake class to act like value types so they can be used with Set semantics: this can be achieved by specifying the :value-type named parameter with a True value.


This functionality is really intended for ad-hoc data structures, as a way to easily prototype or enforce type-checking on some trial code. For production, it is recommended to change each of the Rake cases into an actual class with typed attributes: this will help in performance and future mantainability.

Taking from the example code:

my $foo = Rake[Int,Str,IO].new(42,"bar","filename".IO);
say $foo[0];  # id: 42
say $foo[1];  # name: bar
say $foo[2];  # path: "filename".IO

for production could be written as:

class Foo {
    has Int      $.id;
    has Str      $.name;
    has IO::Path $.path;

my $foo =, :name<bar>, :path("filename".IO));
say $;    # 42
say $;  # bar
say $foo.path;  # "filename".IO

You will thank yourself in the future!


Inspired by the remarks of bobthecimmerian at:


Elizabeth Mattijsen [email protected]

Source can be located at: . Comments and Pull Requests are welcome.


Copyright 2020, 2021 Elizabeth Mattijsen

This library is free software; you can redistribute it and/or modify it under the Artistic License 2.0.