Re: Ada and Unicode

[Thomas <fantome.forums.tDeContes@free.fr.invalid>]

In article 
<fantome.forums.tDeContes-079FD6.18515603042022@news.free.fr>,
 Thomas <fantome.forums.tDeContes@free.fr.invalid> wrote:

> In article <f9d91cb0-c9bb-4d42-a1a9-0cd546da436cn@googlegroups.com>,
>  Vadim Godunko <vgodunko@gmail.com> wrote:
> 
> > On Sunday, April 18, 2021 at 1:03:14 AM UTC+3, DrPi wrote:
> 
> > > What's the way to manage Unicode correctly ? 


> > Ada doesn't have good Unicode support. :( So, you need to find suitable set 
> > of "workarounds".
> > 
> > There are few different aspects of Unicode support need to be considered:
> > 
> > 1. Representation of string literals. If you want to use non-ASCII 
> > characters 
> > in source code, you need to use -gnatW8 switch and it will require use of 
> > Wide_Wide_String everywhere.
> > 2. Internal representation during application execution. You are forced to 
> > use Wide_Wide_String at previous step, so it will be UCS4/UTF32.
> 
> > It is hard to say that it is reasonable set of features for modern world.
> 
> I don't think Ada would be lacking that much, for having good UTF-8 
> support.
> 
> the cardinal point is to be able to fill a 
> Ada.Strings.UTF_Encoding.UTF_8_String with a litteral.
> (once you got it, when you'll try to fill a Standard.String with a 
> non-Latin-1 character, it'll make an error, i think it's fine :-) )
> 
> does Ada 202x allow it ?


hi !

I think I found a quite nice solution!
(reading <t3lj44$fh5$1@dont-email.me> again)
(not tested yet)


it's not perfect as in the rules of the art,
but it is:

- Ada 2012 compatible
- better than writing UTF-8 Ada code and then telling gnat it is Latin-1
  (in this way it would take UTF_8_String for what it is:
  an array of octets, but it would not detect an invalid UTF-8 string,
  and if someone tells it's really UTF-8 all goes wrong)
- better than being limited to ASCII in string literals
- never need to explicitely declare Wide_Wide_String:
  it's always implicit, for very short time,
  and AFAIK eligible for optimization



package UTF_Encoding is

   subtype UTF_8_String is Ada.Strings.UTF_Encoding.UTF_8_String;

   function "+" (A : in Wide_Wide_String) return UTF_8_String
   renames Ada.Strings.UTF_Encoding.Wide_Wide_Strings.Encode;

end UTF_Encoding;


then we can do:


package User is

   use UTF_Encoding;

   My_String : UTF_8_String := + "Greek characters + smileys";

end User;


if you want to avoid "use UTF_Encoding;",
i think "use type UTF_Encoding.UTF_8_String;" doesn't work,
but this should work:


package UTF_Encoding is

   subtype UTF_8_String is Ada.Strings.UTF_Encoding.UTF_8_String;

   type Literals_For_UTF_8_String is new Wide_Wide_String;

   function "+" (A : in Literals_For_UTF_8_String) return UTF_8_String
   renames Ada.Strings.UTF_Encoding.Wide_Wide_Strings.Encode;

end UTF_Encoding;


package User is

   use type UTF_Encoding.Literals_For_UTF_8_String;

   My_String : UTF_Encoding.UTF_8_String
               := + "Greek characters + smileys";

end User;



what do you think about that ? good idea or not ? :-)

-- 
RAPID maintainer
http://savannah.nongnu.org/projects/rapid/