[swift-evolution] API Guidelines: dropFirst?

[Brent Royal-Gordon]

> What is the rationale behind the name dropFirst()? Being a non-mutating method it should clearly be e.g. droppingFirst() according to the API Naming Guidelines.

Like many `Sequence` and `Collection` operations, `dropFirst()` is a result of the "term of art" exception, which is implied by the "Use Terminology Well" section of the API Guidelines: <https://swift.org/documentation/api-design-guidelines/#use-terminology-well>

Many languages use `dropWhatever` or `drop_whatever` for operations which return some sort of list with some of its leading or trailing elements removed. For instance:

* Ruby (which I happen to have in Dash) has `drop(n)` and `drop_while` methods.
* Haskell has `drop n`, `dropWhile`, and `dropWhileEnd` functions.
* Scala has a `drop(n)` method.
* R has a `dropFirst` function.

The standard library has chosen to break its usual patterns in order to maintain consistency with languages like these.

Personally, I believe the term of art exception has been misapplied in this area of the language; the precedents are not very strong, and the resulting APIs form a patchwork of inconsistent names rather than a coherent family. The term of art exception increases the clarity of calls like `map` and `filter` where the names are truly universal, but it impedes the clarity of the whole family of `first`/`prefix`/`suffix`/`last` calls, and the names should be revisited and rationalized. But that hasn't happened yet.

-- 
Brent Royal-Gordon
Architechies