[swift-evolution] sortBy, minElementBy and maxElementBy methods

[Jacob Bandes-Storch]

+1, although I wonder if the method names should be distinct (such as
minElementBy, sortBy, etc.)

On Wed, 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) }
>
>     }
>
> }
>
>
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>
>
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