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 <[email protected]> wrote: > > It confuses people if provide a global function byComparing in stdlib which's > doing nothing alone. > > Dave Abrahams <[email protected] <mailto:[email protected]>> 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 >> <[email protected] >> <javascript:_e(%7B%7D,'cvml','[email protected]');>> 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 >> [email protected] >> <javascript:_e(%7B%7D,'cvml','[email protected]');> >> https://lists.swift.org/mailman/listinfo/swift-evolution >> <https://lists.swift.org/mailman/listinfo/swift-evolution> >
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