[swift-users] How to be DRY on ranges and closed ranges?

[David Hart]

I’ve been bitten by that quite a few times. I’m not a fan of the new distinction between Range and ClosedRange. I understand the reasoning behind them, but the new model is creating more problems for me than the it solves.

David.

> On 12 Oct 2016, at 12:21, Jean-Denis Muys via swift-users <swift-users at swift.org> wrote:
> 
> Hi,
> 
> I defined this:
> 
> func random(from r: Range<Int>) -> Int {
>     let from = r.lowerBound
>     let to =  r.upperBound
>     
>     let rnd = arc4random_uniform(UInt32(to-from))
>     return from + Int(rnd)
> }
> 
> so that I can do:
> 
> let testRandomValue = random(from: 4..<8)
> 
> But this will not let me do:
> 
> let otherTestRandomValue = random(from: 4...10)
> 
> The error message is a bit cryptic:
> 
> “No ‘…’ candidate produce the expected contextual result type ‘Range<Int>’”
> 
> What is happening is that 4…10 is not a Range, but a ClosedRange.
> 
> Of course I can overload my function above to add a version that takes a ClosedRange.
> 
> But this is not very DRY.
> 
> What would be a more idiomatic way?
> 
> Thanks,
> 
> Jean-Denis
> 
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