[swift-evolution] Arrays Returning Optionals instead of Index Out of Bounds

Vladimir.S svabox at gmail.com
Mon Jun 6 12:10:56 CDT 2016

Please find this draft of proposal(hope this is correct link for latest 

The main idea is to introduce 2 new subscript methods:  [clamping:] and 

There was discussion in "[Proposal] More lenient subscript methods over 
Collections" and (older) "[Proposal] Safer half-open range operator"

On 06.06.2016 19:50, Rob Norback via swift-evolution wrote:
> Hi Everyone!
> This is my first time emailing the swift evolution list, so if this topic
> has already been discussed please let me know.  I looked through all the
> accepted and rejected proposals and it doesn't seem to be on there.
> The main thought is that dictionaries return optionals, so why not arrays?
> Or other CollectionTypes for that matter.  I would think this would be the
> expected behavior in this situation:
> var myArray:[String?] = []
> print(myArray[4])
> // EXC_BAD_INSTRUCTION, but could just be Optional(nil)
> Then you could do things like
> if let arrayValue = myArray[4] {
>    // do something
> }
> Of course you could simply check with with the count, but considering
> Swift's use of optionals to represent empty variables rather than erroring
> out or returning an empty String, I think this functionality would be
> appropriate to include in the Swift standard library.
> And there's about 15,000 people who've looked for this functionality in the
> last year:
> http://stackoverflow.com/questions/25329186/safe-bounds-checked-array-lookup-in-swift-through-optional-bindings.
> Please let me know what you think.
> Best,
> Rob Norback
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