The enum class is inspired by enumerated types in other languages,
and draws much of its functionality from the primitive list class.
Generally, enums are more restrictive than lists, with the intent of promoting self-documenting code. They do not allow duplicate values or names, nor do they allow enum values to be changed later.
In essence, an enum can be thought of as a dictionary of values, which can be referenced later down the road with the assurance that the related value will never change.
The enum class is the parent of numeric and generic enums, and will always exist alongside one of the child classes. Which child class an enum will inherit is (generally) decided at run time.
See the pkgdown site for more information.
Generic enums have:
Class attribute of enum and generic_enum
Unique name/value pairs
Explicitly defined values
Any type of value
Numeric enums have:
Class attribute of enum and numeric_enum
Unique name/value pairss
Either explicit or implicitly defined values
All numeric values
Implicit values are created when a name is passed to the enum constructor without a value associated with it. The constructor will then assign the name a value, which is either:
Plus one to the previous index's value
The index of the name
| List | Enum | |
| Primitive | ☑ | x |
| Static | x | ☑ |
| Allow duplicate names | ☑ | x |
| Allow duplicate values | ☑ | x |
| Allow values without names | ☑ | x |
| Implicit definition | x | ☑(Numeric enums) |