Course of Raku / Advanced / More about built-in types / Enumerations 🆕

Defining an enum

Declare an enum with the enum keyword, a name, and the list of constant names:

enum Colour <red green blue>;

This creates a new type, Colour, and three constants: red, green, and blue. You can use the constants directly by name:

say red;   # red
say green; # green

Behind each name is a number, assigned automatically from zero in the order you listed them — red is 0, green is 1, blue is 2. Because the values are ordered, you can compare the constants:

say red < blue; # True

A variable can be typed with the enum, so that it accepts only those constants:

my Colour $c = green;
say $c; # green

If a name might clash with something else in your program, you can always refer to a constant through the enum’s name with :::

say Colour::red; # red

An enum gives a set of related constants a name and a type, which makes code that uses them far clearer than bare numbers. The next topic looks at the numbers behind the names.

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