Course of Raku / Advanced

Introspection with MOP

MOP stands for Meta-object protocol. In Raku, it allows to get additional information about the objects in the program, such as containers or variables.

Condider a type-constrained variable:

my Int $int;

Debugging this variable using .^name reveals its type.

my Int $int;
say $int.^name; # Int

In this program, ^name is a built-in method that returns the type of the value kept in the container. This is a part of the so-called metaobject that contains meta-information about the container.

Here is a modified example from the earlier topic:

my $value;
say $value.^name;

$value = 42;
say $value.^name;

$value = 'fourty-two';
say $value.^name;

This time, the program only prints type names:


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Scalar containers / Default values   |   WHAT and ^name