[swift-evolution] [Pitch] Allow numerical keywords in member references

[Ross O'Brien]

I could see a purpose for identifiers which started numbers but weren't
entirely numerical.
e.g.
enum Dimensions { case `2D`, `3D` }
enum DiceRoll { case d6, `2d6` }
func roll(dice: DiceRoll) -> Int { ... }
roll(.`2d6`)

I'm not sure I see one for identifiers which are entirely numerical.

Ross


On Thu, Mar 9, 2017 at 8:05 AM, Adrian Zubarev via swift-evolution <
swift-evolution at swift.org> wrote:

> My point would be to have a exact set of possible numerical cases. The
> issue with numerical cases is that they don’t have to be ordered and they
> could also be overlapping with other subsystems (by subsystem I mean a
> subsystem of your particular project).
>
> Even if we had the ability to limit the range of numerical types like Int,
> we still might not be able to exclude inner values for that range, which
> makes RawRepresentable not quite efficient to work with. Numerical enum
> cases on the other hand could solve that issue elegantly.
>
> I see the reason for types other because of FP and integer literals, but I
> don’t see why we couldn’t have numerical enum cases.
>
>
>
> --
> Adrian Zubarev
> Sent with Airmail
>
> Am 9. März 2017 um 08:52:34, Slava Pestov (spestov at apple.com) schrieb:
>
>
> On Mar 8, 2017, at 11:46 PM, Adrian Zubarev <adrian.zubarev at devandartist.
> com> wrote:
>
> I don’t have more precise examples except something like TCP socket error
> codes as an enum.
>
> I would expect that the error code is available as a computed property of
> the enum value, perhaps as its raw value or something else. I would not
> expect it to be part of the enum case *name*. What significance does the
> numeric code have to the reader of the code, and when do you ever want to
> permanently freeze error codes in an API like this?
>
> Note that even Unix errno error codes are not standardized across unices
> or even different architectures running Linux; only their names are.
>
> Slava
>
> The example with the number literal is actually really good, because it
> also shows the bad sides of the pitch. However we could allow numerical
> enum cases without any issues right?
>
>
>
> --
> Adrian Zubarev
> Sent with Airmail
>
> Am 9. März 2017 um 08:41:13, Slava Pestov (spestov at apple.com) schrieb:
>
>
> On Mar 8, 2017, at 11:33 PM, Adrian Zubarev via swift-evolution <
> swift-evolution at swift.org> wrote:
>
> I forget to mention, this should be also valid:
>
> let `42` = 42
>
> print(`42`)
>
> struct A {
>     let `0` = 0
> }
>
> let number = A().0
>
>
> -1
>
> This seems really confusing.
>
> extension Int { var `0`: Int { return 0 } }
>
> 3.0 // is this a float literal?
> 3 .0 // member access?
> .0 // this is actually a contextual member access, and not a literal ‘0.0’?
>
>  I’d prefer if .0, .1, … were reserved for tuple fields; .0 is already not
> very descriptive, but at the very least if you see it in source code you
> know you have a tuple type and not something else.
>
> Also the compiler’s name mangling relies on the fact that identifiers
> never begin with a numeric character or symbol.
>
> Can you give a motivating example where allowing an identifier to start
> with a number actually helps readability?
>
> Slava
>
>
>
>
> --
> Adrian Zubarev
> Sent with Airmail
>
> Am 9. März 2017 um 08:24:54, Adrian Zubarev (adrian.zubarev at devandartist.
> com) schrieb:
>
> Hi Swift community, I’d like to pitch this idea again.
>
> Swift already has the pitched feature, but it is exclusive for tuples only.
>  *SE–0071* allowed the use of keywords after the . in a member access,
> except for those keywords that have special meaning by using back-ticks.
> However, members starting with numbers are not special keywords and as
> already mentioned, numerical members are already allowed in tuples.
>
> I propose to extend that capability to the whole language and make that
> behavior consistent. To disambiguate members starting with a number one
> would need to use back-ticks.
>
> // Enum
> enum ErrorCode : String {
>
>     case `2345` = "my description for 2345"
>     case `123a` = "my description for 123a"
>     case `123b` = "my description for 123b"
> }
>
> let code = ErrorCode.2345
>
> // Function
> func `42foo`(label: Type, `12345`: Type, `0987something`: Type) { … }
>
> // Tuple
> (`1`: Int, `2`: Int)
>
> My question is: would that be in scope for Swift 4?
>
>
> --
> Adrian Zubarev
> Sent with Airmail
>
>
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