Patrick, I never said the order of the enum was intrinsic. If the offset of the
case were the truth of the enum as you said enums would be ordinal types and
you could do tests like "Planet.Mercury > Planet.Venus" without any extra code.
But enums are nominal types not ordinal types so you can only distinguish the
different values but they have no particular order or any other property. Two
simple examples of nominal types are colours and cardinal points. Do they have
any particular order? That's how enums are implemented in Swift (as a nominal
type) and that's another reason why working with case names makes even more
sense.
L
-----Original Message-----
From: "Patrick Smith" <[email protected]>
Sent: 02/06/2016 11:18 PM
To: "Leonardo Pessoa" <[email protected]>
Cc: "Brent Royal-Gordon" <[email protected]>; "swift-evolution"
<[email protected]>
Subject: Re: [swift-evolution] Working with enums by name
>From what I understand, enums normally are represented internally by an offset
>— that is their truth. With RawRepresentable enums, you are saying “no, I want
>the truth to be something else”. But it seems that they are still represented
>internally by an offset, so you can’t reorder a RawRepresentable enum’s cases
>and maintain ABI compatibility either.
So what you are saying about the order of cases being an intrinsic part of an
enum does make sense. I’m not sure if can still lead to confusing / fragile
code though.
Patrick
On 2 Jun 2016, at 10:17 PM, Leonardo Pessoa <[email protected]> wrote:
There are several ways to solve this, which IMO is a basic functionality of
enums, writing code that is currently possible and works. But that's the issue,
you still have to write code to have a basic functionally. I don't remember not
being able to do this out-of-the-box in any language I worked with.
L
From: Patrick Smith
Sent: 02/06/2016 02:07 AM
To: Brent Royal-Gordon
Cc: Leonardo Pessoa; swift-evolution
Subject: Re: [swift-evolution] Working with enums by name
Great points Brent. I think the ValuesEnumerable method would be the most
straight forward. Also, the number of cases are likely only going to be in
range of 6–20, so iterating would be fine I think. People can create something
like `Dictionary(Planet.allValues.enumerated().lazy.map{ ($1, $0) })` (I think
that’s right) if they really need.
> On 2 Jun 2016, at 2:40 PM, Brent Royal-Gordon via swift-evolution
> <[email protected]> wrote:
>
> Or the `ValuesEnumerable` proposal would give you a convenient, though
> slightly slow, way to do two-way lookup by order:
>
> enum Planet: String, ValuesEnumerable {
> var order: Int {
> return Planet.allValues.index(of: self)!
> }
> init(order: Int) {
> self = Planet.allValues[order]
> }
> case mercury, venus, …
> }_______________________________________________
swift-evolution mailing list
[email protected]
https://lists.swift.org/mailman/listinfo/swift-evolution
