OptionalIntBinaryFunction
class OptionalIntBinaryFunction<A, OA : ObservableValue<A>, B, OB : ObservableValue<B>>(argA: OA, argB: OB, lambda: (A, B) -> Int?) : BinaryFunction<Int?, A, OA, B, OB> , ObservableOptionalInt
Boilerplate which avoids having to use generics.
Similar to IntBinaryFunction, but the value can also be null.