[swift-evolution] sortBy, minElementBy and maxElementBy methods

[Dave Abrahams]

You don’t.  Is that a problem for the intended use-cases?

-Dave

> On Dec 31, 2015, at 12:11 AM, Susan Cheng <susan.doggie at gmail.com> wrote:
> 
> And how do you write a @noescape version with this function?
> 
> Dave Abrahams <dabrahams at apple.com <mailto: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 <http://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 <https://lists.swift.org/mailman/listinfo/swift-evolution>
>> 
> 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.swift.org/pipermail/swift-evolution/attachments/20151231/5e0748d7/attachment.html>