[swift-evolution] [SR-933] Rename flatten to flattened

Dave Abrahams dabrahams at apple.com
Fri Apr 8 13:28:30 CDT 2016

on Fri Apr 08 2016, Pyry Jahkola <swift-evolution at swift.org> wrote:

>     On 08 Apr 2016, at 13:19, Haravikk via swift-evolution
>     <swift-evolution at swift.org> wrote:
>     I think it makes sense to just rename them; it’s not as though flattened or
>     mapped is somehow far removed from the original meaning as the actual action
>     is the same, it’s just changing tense.
> -1, and not only for the reasons we neither call trigonometric functions `sine`,
> `cosine`, and `tangent`. The existing names are widely known, commonly taught in
> modern introductory programming courses, to the point, and googleable.
> In addition:
>     If we want mutating forms of this methods then I much prefer .map() and .
>     mapped() to .map() and .mapInPlace() or whatever, as the latter contradicts
>     the naming convention used everywhere else which only adds confusion.
> This idea of in-place versions is innocuous but absurd. In general, there's no
> way mapping `T -> U` over a `[T]` could possibly accommodate the result in the
> argument of type `[T]`:
> var xs: [Int] = ...
> xs.mapInPlace {String($0)} // ???

No, you'd just give it a more-restricted signature that only accepted
T->T closures.

> And the same goes for `flatMap`, and `Optional` and others. Likewise, `flatten()
> ` couldn't possibly happen in place because the result type has one level of
> nesting less than the argument.


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