"A singleton [[Tuple]] with the given [[element]] if the given element is non-null, or the [[empty sequence|Empty]] otherwise. This operation transforms an optional type `T?` to a sequence type `[]|[T]` allowing optional values to be the subject of operations defined for [[streams|Iterable]]. For example, [[flat mapping|Iterable.flatMap]] `emptyOrSingleton()` reproduces the behavior of [[Iterable.coalesced]]. The expression { \"1.23\", \"foo\", \"5.67\", \"-1\", \"\" } .map(parseFloat) .flatMap(emptyOrSingleton) produces the stream: { 1.23, 5.67, -1.0 }" see (`class Tuple`, `interface Empty`) tagged("Sequences") shared []|[Element&Object] emptyOrSingleton<Element> (Element element) => if (exists element) then [element] else [];