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

Thorsten Seitz tseitz42 at icloud.com
Sat Jun 11 14:50:05 CDT 2016

> Am 10.06.2016 um 17:22 schrieb Erica Sadun via swift-evolution <swift-evolution at swift.org>:
>> On Jun 10, 2016, at 8:02 AM, Xiaodi Wu via swift-evolution <swift-evolution at swift.org> wrote:
>> On Fri, Jun 10, 2016 at 7:18 AM, Haravikk <swift-evolution at haravikk.me> wrote:
>>>> * The word "where" does not consistently imply `break` or `continue`. In current Swift, `where` implies `break` in the context of a `while` loop and `continue` in the context of a `for` loop. Some users intuitively guess the correct meaning in each context, while others guess the wrong meaning. Therefore, the only way to learn for sure what `where` means in any context is to read the rulebook. That, by definition, means that this is unintuitive.
>>> This is an argument for renaming the where keyword on for loops to be more clear, or to somehow integrate continue/break to be more explicit about what the developer intends for it to do.
>> Sure: I conclude that the keyword should be *either* removed *or* reformed; both outcomes could address the issue.
> This is my stance as well and I reserve the right to flit between both choices until we've fully talked it through.
> One more data point. 
> In the standard library there are just under 950 uses of "for in loops". There are 3 uses of "for in while" :

How many of the 950 "for in loops" use a guard with continue? Only these can be compard with the "for in where loops".


> private/StdlibUnittest/StdlibUnittest.swift.gyb:    for j in instances.indices where i != j {
> public/core/Algorithm.swift:  for value in rest where value < minValue {
> public/core/Algorithm.swift:  for value in rest where value >= maxValue {
> -- Erica
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