[swift-evolution] Request: Multiple Bool signatures

[Erica Sadun]

> On Mar 28, 2016, at 11:16 AM, Dave Abrahams via swift-evolution <swift-evolution at swift.org> wrote:
> 
> 
> on Fri Mar 25 2016, Erica Sadun <swift-evolution at swift.org <mailto:swift-evolution at swift.org>> wrote:
> 
>> I am looking for examples of method/function signatures that use multiple Boolean flags, e.g.
>> 
>> func generateContact(withAddress: Bool, withEmail: Bool, withPhone: Bool) -> Customer // not my code
>> 
>> If you have app code or library code around that you can check, I
>> would greatly appreciate if you can share signatures with me or just
>> generally comment on how often this pattern shows up in your daily
>> life. I am specifically looking for: use of two or more separate
>> Boolean parameters passed as flags.
>> 
>> I would also welcome examples of option sets that replaced Boolean
>> flags with a note as to whether that option set type is used elsewhere
>> in your app.
>> 
>> I am following up to an action item that Brent Royal-Gordon mentioned
>> on-list a while back but I want real supporting motivating code
>> evidence before I move forward with a draft proposal.
>> 
>> Feel free to email me off-list. Thank you,  -- Erica
> 
> It's not hard to grep through Apple's APIs for things like this using
> the repository we put up for the API naming review.
> 
> HTH,

I actually did this. I also pulled down a bunch of Github repos looking for the pattern.

Interestingly what I found was:

* Few circumstances where multiple boolean flags were used, both in Apple code and third party code
* Two flags was the most common multiplicity. Three flags were rare. I did not find any with four or more.
* Code from what I judged as experts that used multiple booleans were primarily initializers, with a few instances from graphics code for things like stroke and fill.
* Code in gists that showed many flag booleans in normal methods were almost always from what I'd rank as "beginner code"

I'm not going to press forward with the language enhancement I had in mind because I don't see a compelling reality-based need for it after performing this check.

-- E
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