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parameterize a record. To implement a Option type, a Boolean type is used as the discriminant; the following example provides a generic to create an option type from any non-limited constrained type:generic -- Any constrained & non-limited type. type Element_Type is private;package Optional_Type is -- When the discriminant, Has_Element, is true there is an element field, -- when it is false, there are no fields (hence the null keyword). type Optional (Has_Element : Boolean) is record case Has_Element is when False => Null; when True => Element : Element_Type; end case; end record;end Optional_Type;

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