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