Subject: Re: Reminder: SG16 telecon tomorrow (Wednesday, 2020-06-10)
From: Hubert Tong (hubert.reinterpretcast_at_[hidden])
Date: 2020-06-10 14:28:13
On Wed, Jun 10, 2020 at 3:08 PM Corentin Jabot <corentinjabot_at_[hidden]>
> On Wed, 10 Jun 2020 at 21:02, Hubert Tong via SG16 <sg16_at_[hidden]>
>> On Wed, Jun 10, 2020 at 2:51 PM Tom Honermann <tom_at_[hidden]> wrote:
>>> On 6/10/20 1:28 PM, Hubert Tong wrote:
>>> This may be useful for an intermediate stage of the process of updating
>>> the wording:
>>> Basic source character set:
>>> set of abstract characters used for the description of source code for
>>> the purposes of this document
>>> I think the "basic source character set" fails to be a "character set".
>>> I believe the elements of a character set are mappings of values to
>>> abstract characters.
>>> I agree with your characterization of a "character set". But, the
>>> members of the "basic source character set" arguably have values on an
>>> implementation-defined basis. Per [cpp.cond]p12
>>> <http://eel.is/c++draft/cpp.cond#12>, the values of character literals
>>> used in a conditional preprocessing directive may have values different
>>> from their values in the execution character set; and if they don't
>>> correspond to the values of the basic source character set members, then I
>>> don't know what else they might correspond to. This may be indicative of
>>> the existence of an additional, currently unnamed, conditionally-defined
>>> character set.
>> Sounds like the last there, except we can simply go with
>> implementation-defined. If could happen to be the same as the execution
>> character set.
> Agreed that going with making these comparison implementation-defined
> there might be the best option. Cleaning that up might be breaking,
> especially as ebcdic encodings
> may not have contiguous values for a-z, A-Z. Would definitively require
> some research
> If we could fix that properly, converting to execution encoding before
> doing the computation would make sense.
I don't know what the effect would be, but we can consider deprecating the
use of character values in preprocessing.
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