[swift-evolution] [Guidelines, First Argument Labels]: Prepositions inside the parens

[Charles Kissinger]

FWIW, I think these new guidelines strike a very nice balance between all of the competing concerns. The result of applying them to some of my own code could best be described as “different but not unpleasant” ;-)

In looking over the diffs, one nice result I didn’t expect is that moving the prepositional phrases into the first argument label seems to increase the speed with which I absorb the general intent of a function -- the “at a glance” understanding -- by moving a “detail” (important as it might be) into the parameter list. (The split prepositional phrases had the opposite effect for me.)

—CK

> On Feb 9, 2016, at 11:18 AM, Dave Abrahams via swift-evolution <swift-evolution at swift.org> wrote:
> 
> 
> Hi everybody,
> 
> Having looked at some examples, the API guidelines working group members
> that were present this morning agreed we really want prepositions inside
> the parentheses of method calls.
> 
> Here are some results for the importer; we're still tuning some of the
> heuristics but overall we feel very good about the preposition
> placement:
> 
>  https://github.com/apple/swift-3-api-guidelines-review/commit/da7e512cf75688e6da148dd2a8b27ae9efcb8821?diff=split
> 
> Note that this is not final wording, but here are the guidelines we're
> working with for first argument labels:
> 
> A. Try to form a grammatical phrase including the first argument and
>   describing the primary semantics at the call site.
> 
> B. The first argument gets a label when and only when:
> 
>   1. It does not form part of a grammatical phrase describing the
>      primary semantics.  For example,
>      ```
>      x.dismiss(animated: y)
>      ```
>      [more examples needed]
>      Note that parameters with defaults never describe the primary
>      semantics. so are always labeled.
>      ```
>      func invert(options options: SomeOptionSet = []) // yes
>      func invert(_ options: SomeOptionSet = [])       // no
>      ```
> 
>   2. The method is a factory method; such calls should mirror
>      initializers, with no preposition.  For example,
>      ```
>      let x = UIColor(red: r, green: g, blue: b)
>      let y = monitor.makeColor(red: r, green: g, blue: b)
>      ```
> 
>   3. It is part of a prepositional phrase
> 
>     a. The label normally starts with the preposition. 
>        For example, 
>        ```
>        x.move(from: a, to: b)
>        x.loadValues(forKeys: ["fox", "box", "lox"])
>        ```
>     b. ...unless the preposition would break a very tight association
>        between parameters:
>        ```
>        x.moveTo(x: a, y: b)
>        ```
>        [encourage grouping parameters into higher-level concepts,
>        e.g. Point, in these cases]
> 
> 
> 
> Feedback most welcome, of course.
> -- 
> -Dave
> 
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