Enumerated types

[timdp]

I just came across a case where I could've used an enum rather than a bunch of constants. Not saying Spider should necessarily have them, but it's worth discussing.

[alongubkin]

Proposal

enum WeekDay {
  sunday = 1,
  monday = 2,
  tuesday = 3,
  wednesday = 4,
  thursday = 5,
  friday = 6,
  saturday = 7
}

var day = WeekDay.sunday;
console.log(day); // => 7

enum Color {
  red, blue, green
}

console.log(Color.red); // => "red"

[Namek]

enum UnitType {
  Unknown = 0,
  Worker = 3
  Soldier, // automatically: = 4
  Car // 5
}

[PhiLhoSoft]

Dart got them recently, in a version simpler than Java (which can associate any arbitrary data to an enum value), but still useful.
Don't forget that enums should be enumerable... Ie. we should be able to loop on the values.
Of course, we can switch on them, too, perhaps with check that all values are covered in the switch.
Can be useful to have two ways to get information from an enum value: its value, and its name.

[alongubkin]

You can loop the values with:

for value of Color { ... }

[Skalman]

Enums might as well reuse the object syntax:

enum WeekDay {
  sunday: 1,
  monday: 2,
  tuesday: 3,
  wednesday: 4,
  thursday: 5,
  friday: 6,
  saturday: 7,
}

What's the advantage of using an enum over a regular object? That it's immutable?

[alongubkin]

@Skalman We can use Object.freeze to make them immutable.

[Namek]

@Skalman look at my example above. Imagine enum with 100 values. I'd like to have them automatically increased.

[Skalman]

@Namek, I meant object-like syntax, i.e. using : instead of =. @alongubkin's Color example would work without modification.

I also prefer @alongubkin's version, where values are strings, not numbers (Color.red == "red", not Color.red == 0)

[Namek]

I also prefer @alongubkin's version, where values are strings, not numbers

@Skalman It's not about a preference. Look at first post once again, both are possible. How do you even use enums not wanting integers in there?

[nmn]

I think enums aren't very useful in a language without type checking. A simple object works just as well in Spider.

In swift enums are useful, as you can use .value syntax and swift already knows which enum you want the value from.

Obviously this feature has no obvious downsides, but it makes sense to keep Spider simple, and avoid features of little value.