[swift-evolution] Proposal: Add SequenceType.first

[Kevin Ballard]

We already don't have a .last on CollectionType and nobody's been
complaining about that. Besides, sequences don't necessarily even
terminate.

-Kevin Ballard

On Wed, Dec 30, 2015, at 04:01 PM, Daniel Duan wrote:
> Users who don’t get the single-pass nature of SequenceType may expect
> a .last as well.
>
>> On Dec 30, 2015, at 3:57 PM, Kevin Ballard via swift-evolution <swift-
>> evolution at swift.org> wrote:
>>
>> It's sometimes useful to get the first element of a sequence. To that
>> end I'd like to propose
>>
>> extensionSequenceType { /// Returns the first element of
>> `self`, or `nil` if `self` is empty. /// - Complexity: O(1) var
>> first: Self.Generator.Element? { var gen = generate() return
>> gen.next()    } }
>>
>> I think it makes sense to add this property to the definition of
>> SequenceType as well, so various sequences can override it to avoid
>> constructing a generator.
>>
>> With this added to SequenceType, we can remove it from
>> CollectionType, as the behavior will be the same.
>>
>> -Kevin Ballard
>>
>> _______________________________________________
>> swift-evolution mailing list swift-evolution at swift.org
>> https://lists.swift.org/mailman/listinfo/swift-evolution
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