[swift-evolution] [Pitch] Retiring `where` from for-in loops

[Xiaodi Wu]

On Mon, Jun 13, 2016 at 10:54 AM, Erica Sadun <erica at ericasadun.com> wrote:

>
> On Jun 13, 2016, at 9:44 AM, let var go via swift-evolution <
> swift-evolution at swift.org> wrote:
>
> I think we must be reading different discussions.
>
> What I have seen in this discussion is the following:
>
> a) The need to filter a for-in loop doesn't arise that often; but,
> b) When it does arise, everyone who has chimed in on this thread (except
> the two people who are proposing the change) thinks that the "where" clause
> is the clearest, most expressive way to do it.
>
>
> As a point of order, may I request you stop singling out "the two people
> who are proposing the change" and discuss the merits of the pitch rather
> than the people involved in the discussion. Details of the Swift community
> code of conduct can be found here:
> https://swift.org/community/#code-of-conduct
>
> As syntactic sugar, the filtering syntax is rarely used, hard to discover,
> and elevates one style (continue if false) above others (continue if false,
> break if true, break if false
>

...and, a surprising number I noted from doing a rough GitHub search (many
more than I thought I would see): return if true, return if false,
fatalError if true, fatalError if false.


> ), which are not expressible using similar shorthand. It introduces a
> fluent style that discourages design comments at the point of use and can
> be difficult to breakpoint during debugging. The recommended alternative
> (using a separate guard) addresses all these points: better commenting,
> better breakpointing and debugging, and fully covers the domain of
> filtering and early exiting.
>
> In response, I'd like to hear why "continue if false" should be
> prioritized above the other options and should be retained, or
> alternatively why the suite should be completed (as in the original
> discussion with "while") in preference to the advantages accrued by guard.
>
> Thank you,
>
> -- Erica
>
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