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

[Dave Abrahams]

on Thu Apr 07 2016, Arsen Gasparyan <swift-evolution at swift.org> wrote:

> Hey guys,
>
> 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?
>
> Implementation: https://github.com/apple/swift/pull/2038

I am agnostic on this, but should explain the rationale for the current
name. It wasn't overlooked.  We kept flatten as is because it is part of
a suite of methods that are terms of art from functional programming
(map, filter, flatMap, reduce) that don't follow the naming guidelines
but we are nonetheless leaving alone.  The fact that the semantics of
flatMap can only be sensibly described in terms of map and flatten
reinforces this rationale.

If we want to change flatten, we should decide whether this is a
principled change, and if so, what the principle is.  If it's a change
simply because “flatten() feels weird,” that's OK too, but we should
understand what we're doing and why.

-- 
Dave