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Re: Pre-RFC: Rename SVf_UTF8 et al.

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From:
Karl Williamson
Date:
August 18, 2021 20:13
Subject:
Re: Pre-RFC: Rename SVf_UTF8 et al.
Message ID:
cc592076-1875-f29a-f1b4-6aa166585d02@khwilliamson.com
On 8/18/21 2:08 PM, Dan Book wrote:
> On Wed, Aug 18, 2021 at 3:50 PM Tomasz Konojacki <me@xenu.pl 
> <mailto:me@xenu.pl>> wrote:
> 
>     On Wed, 18 Aug 2021 13:18:34 -0400
>     Felipe Gasper <felipe@felipegasper.com
>     <mailto:felipe@felipegasper.com>> wrote:
> 
>      > Per recent IRC discussion …
>      >
>      > PROBLEM: The naming of Perl’s “UTF-8 flag” is a continual source
>     of confusion regarding the flag’s significance. Some think it
>     indicates whether a given PV stores text versus binary. Some think
>     it means that the PV is valid UTF-8. Still others likely hold other
>     inaccurate views.
>      >
>      > The problem here is the naming. For example, consider `perl -e'my
>     $foo = "é"'`. In this code $foo is a “UTF-8 string” by virtue of the
>     fact that its code points (assuming use of a UTF-8 terminal)
>     correspond to the bytes that encode “é” in UTF-8. The “UTF-8 flag”,
>     however, is likely *not* set on this string. By contrast, consider
>     `perl -Mutf8 -e'my $foo = "é"'`. Here $foo has the “UTF-8 flag” set,
>     but $foo is NOT a “UTF-8 string” because its code points (in this
>     case, only 1) aren’t valid UTF-8.
>      >
>      > The fact that quite often a “UTF-8 string” lacks the “UTF-8
>     flag”, and a “UTF-8-flagged” string is (usually) *not* a “UTF-8
>     string”, makes little sense except to the “highly initiated”.
>      >
>      > Another problem is “UTF-8” doesn’t really describe the “upgraded”
>     format. This format is what Perl historically called “lax UTF-8” and
>     is now widely called “generalized UTF-8”, which includes unpaired
>     surrogates and code points above Unicode’s maximum.
>      >
>      > PROPOSAL: Rename the following identifiers in code and
>     documentation, leaving macros for the old ones as aliases:
>      > - SVf_UTF8        -> SVf_PVUPGRADED
>      > - SvUTF8          -> Sv_PVUPGRADED
>      > - SvUTF8_on       -> Sv_PVUPGRADED_on
>      > - SvUTF8_off      -> Sv_PVUPGRADED_off
>      > - SvPOK_only_UTF8 -> SvPOK_only_UPGRADED
>      >
>      > Note that flags like REFCOUNTED_HE_KEY_UTF8 do not need a rename
>     because these indicate an actual (if incomplete/invalidated) UTF-8
>     decoding step.
>      >
>      > BENEFITS: Over time, this rename will minimize the confusion
>     between Perl’s upgraded-PV storage format versus UTF-8. The rename
>     may also compel current users of the language who hold mistaken
>     mental models of the flag’s purpose to reexamine their
>     understanding, hopefully for the better.
>      >
>      > POTENTIAL COMPLICATIONS: The mismatch between amended
>     documentation and existing documentation may cause confusion; it
>     should, though, be an auspicious confusion that eventually clarifies
>     rather than misleads.
> 
>     utf8::is_utf8 probably should be renamed too. Anyway, +1 from me.
> 
> Frankly it (and upgrade/downgrade) shouldn't even be in the utf8:: 
> namespace, it's named that for internal reasons not interface reasons.
> 
> -Dan

Upgrade and downgrade tell me nothing.  I don't object to renaming, but 
something better than these needs to be found


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