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

[David Rönnqvist]

I don’t particularly like these name changes. 

I would even go as far as saying that these recent discussions about renaming flatten, map, filter, reduce has made me question the original Swift 3 API renaming. What I mostly like about the current (2.2) naming is that the non-mutating version is the default (for example `sort`/`sortInPlace` compared to `sorted`/`sort`). I feel that switching the default version to be the mutating variant is quite a strong statement on the languages behalf with regards to mutability vs immutability. 

- David

> on Sun Apr 10 2016, Arsen Gasparyan<to.arsen.gasparyan-AT-gmail.com>wrote:
> 
> > Ok. Is it final decision?
> No, any API change needs to go through review on the evolution list.
> Also, FWIW, I am not particularly keen on changing these names.
> 
> > Can I start working on it?
> > 
> > On Sun, 10 Apr 2016 at 23:07, Howard Lovatt via swift-evolution
> > <swift-evolution at swift.org>wrote:
> > 
> > Do it to them all: flatMapped, unioned, etc.
> > 
> > On Monday, 11 April 2016, Dave Abrahams via swift-evolution
> > <swift-evolution at swift.org>wrote:
> > 
> > on Fri Apr 08 2016, Brent Royal-Gordon<swift-evolution at swift.org>
> > wrote:
> > 
> > > > The 'flatten()' method didn't get the Swift 3 API renaming treatment
> > > > it should have, to go along with reversed, sorted, joined, etc.
> > > > As I see Dmitri Gribenko already agree with it but we still have to
> > > > discuss it here. So what do you think?
> > > 
> > > I'm in favor.
> > > 
> > > Though all of these things are terms of art, not all terms of art are
> > created equal. For instance:
> > > 
> > > * `map` is supported by virtually any language which have any of these
> > > higher-order functions, and to my knowledge the name `map` is
> > > universally used.
> > > * `reduce` is not quite as universally supported, but it's still very
> > > common, and most (but not quite all) languages with higher-order
> > > functions support it.
> > > * `filter` is very widely supported, but the *name* `filter` is not
> > > quite so consistent. Ruby, for instance, calls it `select`, Perl calls
> > > it `grep`, etc.
> > > * `takeWhile` lies on the other end of the spectrum, being very
> > narrowly supported.
> > > 
> > > In my opinion, it would be a really bad idea to rename `map` or
> > > `reduce`; `filter` is probably a bad idea but not terrible; but we
> > > should feel relatively free to rename `takeWhile`.
> > > 
> > > `flatten` is nowhere near as weak a term of art as `takeWhile`, but I
> > > think it still falls towards that end of the spectrum. We shouldn't
> > > worry too much about changing it. `map`, `reduce`, and `filter` are
> > > much stronger terms, and we should be more cautious about changing
> > > them.
> > 
> > The problem is flatMap. The semantics of map, flatMap, and flatten are
> > inextricably linked. IMO it would be weird to do this to one or two of
> > these names and not to all of them.
> > 
> > --
> > Dave
> > 
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> > 
> > --
> > -- Howard.
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> --
> Dave
> 
> 
>