Sure, that's a good idea, though I'd personally use the signum var, since using
rawValue seems like a bit of an abuse of the fact the enum is defined this way
and doesn't help readability of the code:
enum IntegerSign<NumberType: SignedNumberType>: RawRepresentable {
case Negative
case Zero
case Positive
init?(rawValue: NumberType) {
if rawValue == -1 {
self = .Negative
} else if rawValue == 0 {
self = .Zero
} else if rawValue == 1 {
self = .Positive
} else {
return nil
}
}
var rawValue: NumberType {
return self.signum
}
var signum: NumberType {
switch self {
case .Negative:
return -1 as NumberType
case .Zero:
return 0 as NumberType
case .Positive:
return 1 as NumberType
}
}
}
extension SignedNumberType {
var sign: IntegerSign<Self> {
if self == 0 {
return .Zero
} else if self > 0 {
return .Positive
} else {
return .Negative
}
}
}
> On May 24, 2016, at 6:09 AM, David Sweeris <[email protected]> wrote:
>
> Can we make it RawRepresentable? That way signum can just return self.rawValue
>
> Sent from my iPhone
>
> On May 23, 2016, at 06:05, Charlie Monroe via swift-evolution
> <[email protected] <mailto:[email protected]>> wrote:
>
>> The clean way would be to make it an enum with var signum that would return
>> -1, 0, 1:
>>
>> enum IntegerSign<NumberType: SignedNumberType> {
>>
>> case Negative
>> case Zero
>> case Positive
>>
>> var signum: NumberType {
>> switch self {
>> case .Negative:
>> return -1 as NumberType
>> case .Zero:
>> return 0 as NumberType
>> case .Positive:
>> return 1 as NumberType
>> }
>> }
>>
>> }
>>
>> extension SignedNumberType {
>> var sign: IntegerSign<Self> {
>> if self == 0 {
>> return .Zero
>> } else if self > 0 {
>> return .Positive
>> } else {
>> return .Negative
>> }
>> }
>> }
>>
>> Charlie
>>
>>> On May 23, 2016, at 9:29 AM, Haravikk via swift-evolution
>>> <[email protected] <mailto:[email protected]>> wrote:
>>>
>>> Could you give an example of this method’s usage? Surely your value is
>>> either positive, negative or zero already, so this method doesn’t return
>>> anything more useful.
>>>
>>> In other words, anywhere that I might do this:
>>>
>>> if myValue.sign > 0 { … }
>>>
>>> I could just as easily do:
>>>
>>> if myValue > 0 { … }
>>>
>>> To the same end result surely? Unless I’m missing something it seems
>>> redundant.
>>>
>>> If there is a use-case for this, would it make more sense to have the
>>> return type as an enum with cases for Positive, Negative and Zero?
>>>
>>>> On 22 May 2016, at 08:07, Adam Nemecek via swift-evolution
>>>> <[email protected] <mailto:[email protected]>> wrote:
>>>>
>>>> Howdy,
>>>> I think that the SignedNumberType should implement a method called sign
>>>> that will return -1 for negative numbers, 0 for 0 and 1 for positive
>>>> numbers. This is similar to the signum method in e.g. Java and similarly
>>>> called methods in other languages.
>>>>
>>>> The implementation is fairly straight forward
>>>>
>>>> extension SignedNumberType {
>>>> var sign: Self {
>>>> if self == 0 {
>>>> return 0
>>>> }
>>>> else if self > 0 {
>>>> return 1
>>>> }
>>>> return -1
>>>> }
>>>> }
>>>>
>>>> I was trying to implement is without branching by doing (x > 0) - (x < 0)
>>>> but I couldn't get the types right so I'm open to suggestions.
>>>>
>>>>
>>>> _______________________________________________
>>>> swift-evolution mailing list
>>>> [email protected] <mailto:[email protected]>
>>>> https://lists.swift.org/mailman/listinfo/swift-evolution
>>>> <https://lists.swift.org/mailman/listinfo/swift-evolution>
>>>
>>> _______________________________________________
>>> swift-evolution mailing list
>>> [email protected] <mailto:[email protected]>
>>> https://lists.swift.org/mailman/listinfo/swift-evolution
>>> <https://lists.swift.org/mailman/listinfo/swift-evolution>
>>
>> _______________________________________________
>> swift-evolution mailing list
>> [email protected] <mailto:[email protected]>
>> https://lists.swift.org/mailman/listinfo/swift-evolution
>> <https://lists.swift.org/mailman/listinfo/swift-evolution>
_______________________________________________
swift-evolution mailing list
[email protected]
https://lists.swift.org/mailman/listinfo/swift-evolution
