Unused

public enum Unused : Plotable

An empty dummy shorthand for a non-utilized generic Plotable type.

This type is a placeholder that can be used in cases where you don’t use all generic types provided by a particular trace. It (hopefully) improves readability and clarifies intent of the source code in these situations.

For example, the Box trace requires specification of three generic types for YData, XData and QData.

let box = Box<[Double], Unused, Unused>(
    y: [1.9, 2.1, 2.2, 2.1]
)

Most of the time one uses either one of XY or Q, but not both at the same time. To create an instance, one would have to come up with some dummy type for XData and QData that conforms to the Plotable protocol. This very likely confuses the potential reader because the corresponding XData/QData attribute is never set and never used.