[swift-evolution] sortBy, minElementBy and maxElementBy methods

[Susan Cheng]

What's problem of overloading? We only have four methods to do so.

Dave Abrahams <dabrahams at apple.com> 於 2016年1月1日星期五 寫道：

>
> On Dec 31, 2015, at 4:14 AM, Tino Heth <2th at gmx.de
> <javascript:_e(%7B%7D,'cvml','2th at gmx.de');>> wrote:
>
>
> func byComparing<T, U: Comparable>(getComparisonKey: (T)->U) -> (T, T) ->
> Bool {
>   return { getComparisonKey($0) < getComparisonKey($1) }
> }
>
> I've written something similar to bring file URLs into the order of their
> creation dates.
> It is a small extension for collection types, and its only downside will
> disappear as soon as properties are accessible via method calls (afair
> there is a proposal in the making).
>
> It was quite a lot fiddling with generics, and I don't have the tiny piece
> of code on my own computer, but it works in a way that you can do
> let sorted =
> array.sortUsingAccessor(ElementType.methodThatReturnsComparable)
> Beside the problems with properties, I really liked that approach.
>
>
> This seems to be essentially the same design as Susan’s, and has the same
> problem: it requires a new overload for every algorithm that takes a
> comparison predicate.
>
> -Dave
>
>
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