[swift-evolution] Proposal: pattern match based on associated value(s) only

[Amir Michail]

> On Feb 23, 2016, at 7:27 AM, Taras Zakharko <taras.zakharko at uzh.ch> wrote:
> 
> I think that other designs (e.g. using classes/structs/protocols) offer a much better solution for this particular problem
> 

That might be more work than just listing all the cases...

>> On 23 Feb 2016, at 13:17, Amir Michail via swift-evolution <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
>> 
>>> 
>>> On Feb 22, 2016, at 10:11 PM, Brent Royal-Gordon <brent at architechies.com <mailto:brent at architechies.com>> wrote:
>>> 
>>>> For example:
>>>> 
>>>> enum Color {
>>>> 	...
>>>> }
>>>> 
>>>> enum Vehicle {
>>>> 	case Car(Color)
>>>> 	case Motorcycle(Color)
>>>> 	...
>>>> }
>>>> 
>>>> switch vehicle {
>>>> 	case _(.Red): … // pattern match based on associated value only
>>>> }
>>> 
>>> As usual, Amir: 
>>> 
>>> 1. Why do you want this feature?
>> 
>> In this example, if there are many kinds of vehicles, it would be annoying to have to write a case for each one to match associated value .Red.
>> 
>>> 
>>> 2. What's actually wrong with the status quo?
>>> 
>> 
>> What would that be for this example? Many cases?
>> 
>>> 3. Can you talk about a non-toy example you've encountered where it would have made your code better?
>>> 
>>> 4. Can you talk about the proposed design in a little more detail? Are there weird edge cases, and how would you handle them? (In the case of this feature, here's one I see: Suppose you have two different associated value types but they both have a .Red case. What happens then?)
>>> 
>>> A half-dozen-word subject line and a code example simply aren't enough to evaluate a proposal. Without knowing exactly what you're proposing and why you think it's a good idea, we can't really evaluate it properly.
>>> 
>>> -- 
>>> Brent Royal-Gordon
>>> Architechies
>>> 
>> 
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