[swift-evolution] sortBy, minElementBy and maxElementBy methods

[Susan Cheng]

And how do you write a @noescape version with this function?

Dave Abrahams <dabrahams at apple.com> 於 2015年12月31日星期四 寫道：

> I don’t understand that argument.  Obviously the function would be
> documented and there would be examples showing how to use it.  Why would it
> confuse people?
>
> I think you’d need much stronger reasons to justify adding an unbounded
> set of overloads (is every algorithm that takes a comparison closure going
> to get one of these?) when we can handle the problem economically with a
> single function.
>
> -Dave
>
> On Dec 31, 2015, at 12:04 AM, Susan Cheng <susan.doggie at gmail.com
> <javascript:_e(%7B%7D,'cvml','susan.doggie at gmail.com');>> wrote:
>
> It confuses people if provide a global function byComparing in stdlib
> which's doing nothing alone.
>
> Dave Abrahams <dabrahams at apple.com
> <javascript:_e(%7B%7D,'cvml','dabrahams at apple.com');>> 於 2015年12月31日星期四
> 寫道：
>
>> Why add all those algorithms when you can write this
>>
>> func byComparing<T, U: Comparable>(getComparisonKey: (T)->U) -> (T, T) ->
>> Bool {
>>   return { getComparisonKey($0) < getComparisonKey($1) }
>> }
>>
>> peoples.sort(byComparing { $0.name })
>>
>> ?
>>
>> -Dave
>>
>> On Dec 30, 2015, at 10:38 PM, Susan Cheng via swift-evolution <
>> swift-evolution at swift.org> wrote:
>>
>>
>> Consider the follows:
>>
>> struct Person {
>>
>>     var name: String
>>     var age: Int
>> }
>>
>> let peoples = [Person(name: "Hawk", age: 24), Person(name: "Andrew",
>> age: 23)]
>>
>> let youngest = peoples.minElement { $0.age < $1.age }
>>
>> print(youngest?.name)
>>
>> it's silly that we always have to write the code like { $0.some < $1.some }
>> or { some($0) < some($1) }
>>
>> so, we should add those methods to stdlib:
>>
>> extension SequenceType {
>>     /// Returns the minimum element in `self` or `nil` if the sequence
>> is empty.
>>     ///
>>     /// - Complexity: O(`elements.count`).
>>     ///
>>     @warn_unused_result
>>     public func minElement<R : Comparable>(@noescape by:
>> (Generator.Element) throws -> R) rethrows -> Generator.Element? {
>>         return try self.minElement { try by($0) < by($1) }
>>     }
>>     /// Returns the maximum element in `self` or `nil` if the sequence
>> is empty.
>>     ///
>>     /// - Complexity: O(`elements.count`).
>>     ///
>>     @warn_unused_result
>>     public func maxElement<R : Comparable>(@noescape by:
>> (Generator.Element) throws -> R) rethrows -> Generator.Element? {
>>         return try self.maxElement { try by($0) < by($1) }
>>     }
>> }
>>
>> public extension MutableCollectionType {
>>
>>     /// Return an `Array` containing the sorted elements of `source`.
>>     /// according to `by`.
>>     ///
>>     /// The sorting algorithm is not stable (can change the relative
>> order of
>>     /// elements that compare equal).
>>     @warn_unused_result(mutable_variant="sortInPlace")
>>     func sort<R : Comparable>(@noescape by: (Generator.Element) -> R) ->
>> [Generator.Element] {
>>         return self.sort { by($0) < by($1) }
>>     }
>> }
>>
>> public extension MutableCollectionType where Self.Index :
>> RandomAccessIndexType {
>>
>>     /// Sort `self` in-place according to `by`.
>>     ///
>>     /// The sorting algorithm is not stable (can change the relative
>> order of
>>     /// elements that compare equal).
>>     mutating func sortInPlace<R : Comparable>(@noescape by: (Generator.
>> Element) -> R) {
>>         self.sortInPlace { by($0) < by($1) }
>>     }
>> }
>>
>> _______________________________________________
>> swift-evolution mailing list
>> swift-evolution at swift.org
>> https://lists.swift.org/mailman/listinfo/swift-evolution
>>
>>
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-evolution/attachments/20151231/c82c58ce/attachment.html>