I've thought about it for a few days, and really like `reduce(mutating:_)`.
I'm not a fan of this. It reads in a way that makes it seem like the parameter should be inout, but it isn't. A variation of reduce where the initial value parameter *is* inout is perfectly sensible (whether or not we want it in the standard library). With that in mind, I don't think we should use this name.
Unfortunately I don't have a better suggestion. I think it was Brent who suggested "mutatingCopyOf" which is more accurate, but also undesirably verbose.
···
Sent from my iPad
On Jan 24, 2017, at 1:54 AM, Chris Eidhof via swift-evolution <swift-evolution@swift.org> wrote:
I've updated the PR, and am now happy for this to go into review.
Reduce with inout by chriseidhof · Pull Request #587 · apple/swift-evolution · GitHub
On Mon, Jan 23, 2017 at 8:27 AM, Russ Bishop <xenadu@gmail.com> wrote:
On Jan 22, 2017, at 10:56 PM, Chris Eidhof <chris@eidhof.nl> wrote:
Not as a direct reply to Russ, but just to reiterate: to me, there are two clear benefits of using the `inout` version of reduce:
1. The performance (currently discussed at length)
2. Readability (because we can use mutating methods on `inout` arguments).Even if the compiler were to optimize the unnecessary copy of `return arr + [el]` away, there are still a lot of other mutable methods that you might want to use within the reduce closure. So I think the proposal is still very valid even if the compiler optimizations would magically appear tomorrow.
To push this proposal forward a little bit, I'd like to come up with a good name. It seems like we shouldn't overload `reduce`, but choose a different name, so that we don't stress the typechecker. Any other suggestions?
On Mon, Jan 23, 2017 at 7:11 AM, Russ Bishop <xenadu@gmail.com> wrote:
--
Chris EidhofSorry for the derail!
reduce(mutating:_:) { } is still my favorite; You can take mutating to mean we will copy the value now but mutate it later.
Some alternatives:
reduce(forMutating:_:) { }
reduce(forInout:_:) { }
reduce(initial:_:) { }
reduce(copying:mutate:) { }
// just kidding...
reduce(copyForLaterMutating:_:) { }It should definitely be some form of reduce.
Russ
--
Chris Eidhof
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