Course of Raku / Advanced / Modules / Packages and namespaces 🆕

Packages and modules

The package keyword introduces a namespace. Anything declared inside it with our becomes part of that namespace and can be reached from outside through the package’s name and the :: separator:

package Maths {
    our $pi = 3.14;
    our sub double($x) { $x * 2 }
}

say $Maths::pi;         # 3.14
say Maths::double(5);   # 10

The variable is reached as $Maths::pi — the sigil, then the package name, then the variable name. A subroutine is called as Maths::double(...).

Both package and module create a namespace; they differ in what else they do. A module is the usual choice for a unit of reusable code, while a plain package is just the namespace with nothing extra. (A class, which you will meet in the next part, creates a namespace too and adds object-oriented machinery on top.)

module Greet {
    our sub hello { 'hi' }
}

say Greet::hello; # hi

So the namespace you have been getting from module is the same mechanism a package provides on its own. Choosing between them is mostly about intent: module for libraries, package for a bare namespace — and, once you reach objects, class for types.

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