Returns the smallest interval containing the inputs (which can include intervals). Typically, the returned interval is not empty. See span(Sequence) and span(List)

- interval -- construct an interval
- span(Sequence) -- construct smallest interval
- span(List) -- construct smallest interval
- toRRi -- construct an interval

- span(List) -- construct smallest interval
- span(Sequence) -- construct smallest interval

The object span is a method function with a single argument.