[swift-evolution] [Proposal] Refining Identifier and Operator Symbology

Fri Oct 21 15:10:42 CDT 2016

A few other thoughts:

* One of our (or at least my) overarching goals for this proposal is to
refine identifier and operator sets by moving away from an ad-hoc
character-by-character approach to a systematic treatment that relies on
well-defined criteria to select blocks of characters for inclusion. My
personal opinion is that reverting to discussions of individual characters,
such as the turned ampersand, means we're simply re-shuffling the current
set of identifier and operator characters to a different one, having failed
to discover any systematic basis for doing so. I think one of the strongest
parts of this proposal is the straight-up statement that identifier start
characters shall be IDC_Start and identifier continuation characters shall
be IDC_Continue, modulo a few ASCII characters that require special
treatment in Swift.

* Particularly if the community insists on emoji being identifiers, we will
have to critically evaluate how to proceed on that in tandem with
operators, because there exist emojified operators and arrows, and certain
emoji are encoded in blocks that are otherwise symbols, which Unicode is
likely to deem as operators in the future. Moreover, IIUC, certain
codepoints can be either emoji or non-emoji symbols and variant selectors
can specify which they are, but in the absence of a variant selector
*either* the emoji or non-emoji version can be correctly displayed
depending on the platform. For some of these, the non-emoji version is
either clearly or plausible an operator character. Therefore, without
dealing *very* carefully with emoji and with operators at the same time, we
are failing to address a key motivation of this proposal, which is to fix
the incorrect separation between emoji operators and emoji identifiers.

On Fri, Oct 21, 2016 at 2:36 PM, Xiaodi Wu <xiaodi.wu at gmail.com> wrote:

> I disagree pretty strongly with this approach. Firstly because as you've
> pointed out, changes to the operator characters will have effects on valid
> operator character sets, secondly because a major question about operators
> is whether it is feasible or no to manually exclude empty set and infinity
> given that Unicode is likely to reject that approach. For these reasons I
> feel very strongly that the reforming the operator and identifier
> characters must move in tandem.
>
> On Fri, Oct 21, 2016 at 14:28 Nevin Brackett-Rozinsky via swift-evolution <
> swift-evolution at swift.org> wrote:
>
>> I think it is important that we as a community discuss the non-operator
>> portion of this proposal. And, given the strong opinions about operators
>> that have been expressed, I think it is unlikely we will do so while major
>> operator changes are on the table.
>>
>> Thus I would suggest that either the operator changes should be separated
>> out into their own proposal, or we should make only minor (and generally
>> consensus-agreed) changes to the operator set as part of this one.
>>
>> Here is what I propose:
>>
>> Emoji shall be identifiers, not operators.
>> The turned ampersand shall be an operator, not an identifier.
>> The empty set and infinity symbols shall be identifiers, not operators.
>>
>> All other potential changes to the set of operator characters then go in
>> their own proposal, which I am sure will receive a lot of attention.
>>
>> It may turn out that the non-operator portion of this proposal
>> nonetheless touches characters that Swift has designated for operators, in
>> which case we may address those as they arise.
>>
>> Does that sound like a reasonable way forward?
>>
>> Nevin
>>
>>
>>
>> On Fri, Oct 21, 2016 at 9:27 AM, Ben Rimmington via swift-evolution <
>> swift-evolution at swift.org> wrote:
>>
>>
>> > On 21 Oct 2016, at 13:42, Benjamin Spratling wrote:
>> >
>> > Brackets and symbols are definitely operators.  Different brackets are
>> used to represent various quantum mechanical forms and operations.
>>
>> The brackets are mostly "bracket pieces":
>>
>>         [:Math_Symbol:]
>>         - [:name=/\bANGLE\b/:]
>>         - [:Emoji:]
>>         - [:ID_Continue:]
>>         - [:NFC_Quick_Check=No:]
>>         & [:Script_Extensions=Common:]
>>         & [:Block=Miscellaneous_Technical:]
>>
>> <http://www.unicode.org/cldr/utility/list-unicodeset.jsp?a=
>> %5B%3AMath_Symbol%3A%5D%0D%0A-+%5B%3Aname%3D%2F%5CbANGLE%
>> 5Cb%2F%3A%5D%0D%0A-+%5B%3AEmoji%3A%5D%0D%0A-+%5B%3AID_
>> Continue%3A%5D%0D%0A-+%5B%3ANFC_Quick_Check%3DNo%3A%5D%
>> 0D%0A%26+%5B%3AScript_Extensions%3DCommon%3A%5D%0D%0A%26+%5B%3ABlock%
>> 3DMiscellaneous_Technical%3A%5D>
>>
>> > Arrows are also useful as operators, including but not restricted to
>> chemical reactions.
>>
>> Including arrows, there are 740 operators:
>>
>>         [:Math_Symbol:]
>>         - [:name=/\bANGLE\b/:]
>>         - [:name=EMPTY SET:]
>>         - [:name=INFINITY:]
>>         - [:Emoji:]
>>         - [:ID_Continue:]
>>         - [:NFC_Quick_Check=No:]
>>         & [:Script_Extensions=Common:]
>>         & [[:Block=Arrows:]
>>            [:Block=General_Punctuation:]
>>            [:Block=Latin_1_Supplement:]
>>            [:Block=Mathematical_Operators:]
>>            [:Block=Miscellaneous_Mathematical_Symbols_A:]
>>            [:Block=Miscellaneous_Symbols_And_Arrows:]
>>            [:Block=Supplemental_Arrows_A:]
>>            [:Block=Supplemental_Arrows_B:]
>>            [:Block=Supplemental_Mathematical_Operators:]]
>>
>> <http://www.unicode.org/cldr/utility/list-unicodeset.jsp?a=
>> %5B%3AMath_Symbol%3A%5D%0D%0A-+%5B%3Aname%3D%2F%5CbANGLE%
>> 5Cb%2F%3A%5D%0D%0A-+%5B%3Aname%3DEMPTY+SET%3A%5D%0D%
>> 0A-+%5B%3Aname%3DINFINITY%3A%5D%0D%0A-+%5B%3AEmoji%3A%5D%
>> 0D%0A-+%5B%3AID_Continue%3A%5D%0D%0A-+%5B%3ANFC_Quick_
>> Check%3DNo%3A%5D%0D%0A%26+%5B%3AScript_Extensions%3DCommon%
>> 3A%5D%0D%0A%26+%5B%5B%3ABlock%3DArrows%3A%5D%0D%0A+++%5B%
>> 3ABlock%3DGeneral_Punctuation%3A%5D%0D%0A+++%5B%3ABlock%
>> 3DLatin_1_Supplement%3A%5D%0D%0A+++%5B%3ABlock%
>> 3DMathematical_Operators%3A%5D%0D%0A+++%5B%3ABlock%
>> 3DMiscellaneous_Mathematical_Symbols_A%3A%5D%0D%0A+++%5B%
>> 3ABlock%3DMiscellaneous_Symbols_And_Arrows%3A%5D%0D%0A+++%5B%3ABlock%
>> 3DSupplemental_Arrows_A%3A%5D%0D%0A+++%5B%3ABlock%
>> 3DSupplemental_Arrows_B%3A%5D%0D%0A+++%5B%3ABlock%
>> 3DSupplemental_Mathematical_Operators%3A%5D%5D>
>>
>> -- Ben
>>
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>>
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