Enumerations

enum Foo {
    A,
    B,
    C,
}

function is_a(v enum Foo) {
    match v {
        Foo::A => return true,
        _ => return false,
    }
}

Enumerations are a set of unique identifiers grouped under a single name. They are defined in a top level enum declaration. An enumeration literal is the name of the enumeration and the name of the item separated by ::. So Foo::A is the A value of Foo, and is distinct from Bar::A.

The only valid operation you can perform with an enumeration is equality, either through the == operator, or via the match statement. This comparison is only valid for enums of the same type. Comparing Foo::A to Bar::A should be a compile-time error or run-time exception.

See also the enum top-level declaration.