[swift-evolution] [Review] SE-0144: Allow Single Dollar Sign as a Valid Identifier

[Jacob Bandes-Storch]

Proposal link:

        https://github.com/apple/swift-evolution/blob/master/propo
sals/0144-allow-single-dollar-sign-as-valid-identifier.md


>         * What is your evaluation of the proposal?
>

-1.

The proposal does not actually provide motivation for keeping $ beyond "the
Dollar library already uses it".

A more Swifty way for a library to introduce these operations would be with
extensions. Here are some suggestions, based off the first several
operations described in the library's readme:

$.at → convenience subscript(Index...) for Collection
$.chunk → convenience function for Sequence
$.compact → flatMap{$0}
$.contains → already exists as Sequence.contains
$.cycle → convenience function for Collection
$.difference → convenience function on Collection, or just use Set
operations, or filter
$.each → exists as Sequence.forEach
$.every → extension on Sequence
$.factorial → convenience method or postfix operator for Integer
$.fetch → convenience function on Collection
and so on.

It looks like the author's Cent <https://github.com/ankurp/Cent> library is
already taking this approach.



>         * Is the problem being addressed significant enough to warrant a
> change to Swift?
>

Yes, but the change has already been made: removing $ as a valid identifier
;-)



>         * Does this proposal fit well with the feel and direction of Swift?
>

Not really. If anything, IMO, the dollar sign feels more like an operator
character. (However, it's probably here to stay in identifiers because of
closure parameters and LLDB variables.)



>         * If you have used other languages or libraries with a similar
> feature, how do you feel that this proposal compares to those?
>

The Dollar library resembles the style of JavaScript libraries such as
jQuery or Underscore, but that isn't a positive thing in my mind — as
mentioned above, the Swift way of doing things is different.



>         * How much effort did you put into your review? A glance, a quick
> reading, or an in-depth study?
>

Thorough reading of the proposal; brief glance at the library's readme on
GitHub.  Lots of time thinking about operator & identifier characters for a
forthcoming proposal.
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