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Example usage: package Optional_Integers is new Optional_Type (Element_Type => Integer); Foo : Optional_Integers.Optional := (Has_Element => True, Element => 5); Bar : Optional_Integers.Optional := (Has_Element => False);

Agda

In Agda, the option type is named with variants and .

ATS

In ATS, the option type is defined as

datatype option_t0ype_bool_type (a: t@ype+, bool) = | Some(a, true) of a | None(a, false)stadef option = option_t0ype_bool_typetypedef Option(a: t@ype) = [b:bool] option(a, b)

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