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