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9. Enumerations

Enumerations define a type whose values come from a fixed set of named cases. They are useful when you want to model a small closed set of states or options.

An enumeration is defined like:

enum State:
    ON
    OFF
end

And used as follows:

s1 := State.ON
s2 := State.OFF
assert(s1 != s2)
assert(s1 == State.ON)

Enumeration values are qualified with the enum name, so State.ON and State.OFF are distinct values of the type State.

Enums work naturally with control flow:

func is_on(s):
    if s == State.ON:
        return true
    end
    return false
end

Use enums when the possible values are known in advance and do not need to carry additional data. If each case needs associated values, variants are the more general construct.

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