Is there any object-oriented static typed language with variables with few types?

Question

I like reading about programming theories, so could you tell me if there is any object-oriented static typed language that allow variables to have a few types? Example in pesudocode:

var value: BigInteger | Double | Nil

I think about way of calling methods on this object. If object value have type BigInteger | Double language could allow user to call only shared methods (lake plus, minus) but when the type is BigInteger | Double | Nil then object of Nil hasn't methods plus and minus, so we can't do anything usefull with this object, because it has only few shared methods (like toString).

So is there any idea how should work calling methods on variable with few types in static typed object-oriented language?

Answer 1

What you are describing is an intersection type. They do exist in Java, for example, but they only arise within the type-checker as the result of capture conversion and type-inference. You cannot write one yourself.

I don't know of any language which uses them directly, but they are often used to describe or analyze type systems of languages, espececially languages which don't actually have a type system. For example, Diamondback Ruby, which is a static type system and type-inferencer for the dynamically typed Ruby programming language, uses both union and intersection types.

Note that the syntax you are using is generally used to denote union types, which are the dual of intersection types. Intersection types are generally written A & B & C.