Transform rule syntax clarifications

[Martin J. Dürst via CLDR-Users]

On 2019/11/18 17:22, Mark Davis ☕️ wrote:
> It should use A∖B when taking about the math operation. Could you file a
> ticket?

Done.   Regards,   Martin.

> {phone}
> 
> On Mon, Nov 18, 2019, 04:42 Martin J. Dürst via CLDR-Users <
> cldr-users at unicode.org> wrote:
> 
>> On 2019/11/17 11:37, Richard Wordingham via CLDR-Users wrote:
>>> On Sat, 16 Nov 2019 13:18:00 -0800
>>> Cameron Dutro via CLDR-Users <cldr-users at unicode.org> wrote:
>>>
>>>> The other bits of syntax you've mentioned are from the Unicode Set
>>>> specification, which you can find in UTS #35
>>>> <https://unicode.org/reports/tr35/#Unicode_Sets>. Unicode Sets are
>>>> like regex character classes, but as you've noticed, there are a
>>>> couple of special operations they support that regexes don't.
>>>> Specifically, the "-" operator is the symmetric difference
>>>> <https://en.wikipedia.org/wiki/Symmetric_difference> between the two
>>>> operands (UTS 35 says "asymmetric difference," but I don't think
>>>> that's a thing - I can't find any definition of it online).
>>>
>>> It very much is a thing!
>>
>> Well, yes, except that it's usually just called "set difference" without
>> an explicit adjective. (I'd strongly suggest that UTS 35 put the word
>> 'asymmetric' in parentheses.) Also, one wouldn't use the symbol '-' for
>> symmetric difference.
>>
>> Regards,   Martin.
>>
>>> In this particular case,
>>>
>>> $accent_minus = [[$accent]-[$iotasub$macron]];
>>>
>>> is probably the same as the symmetric difference, because from
>>> the names i think everything in the second set is in the first set, but
>>> this doesn't always apply.  [abcd] - [abef] is [cd], not the symmetric
>>> difference [cdef].
>>>
>>> Richard.
>