Re: Why no Ada.Wide_Directories?

["J-P. Rosen" <rosen@adalog.fr>]

Le 20/10/2011 09:37, Dmitry A. Kazakov a �crit :
> On Wed, 19 Oct 2011 16:43:08 -0500, Randy Brukardt wrote:
> 
>> > The only way to safely use a UTF-8 string is opaquely, which means you can 
>> > store it whole, but any operation on it is performed after decoding it. 
>> > That's of course the best argument for having it be a separate type.
> Yes. It is worth to remember that Ada once was considered a strongly typed
> language...
> 
Different types represent things that are of different nature. It is not
obvious that a difference in /encoding/ is sufficient to say that two
things are of different nature.

Consider also the problem with files. Is a UTF-8 file a text file? Do
you want a UTF8_IO package? Normally, a UTF-8 file starts with a BOM in
the first line, telling that the whole file is UTF8. How would you read
that? Excerpt from AI137:
---
When reading a file, a BOM can be expected as starting the first line
of the file, but not subsequent lines. The proposed handling of BOM
assumes the following pattern:

1) Read the first line. Call function Encoding on that line with an
   appropriate default to use if the line does not start with a
   BOM. Initialize the encoding scheme to the value returned by the
   function.

2) Decode all lines (including the first one) with the chosen encoding
   scheme. Since the BOM is ignored by Decode functions, it is not
   necessary to slice the first line specially.
---

A possible alternative solution could be to make UTF_8_String a type
derived from String (rather than a subtype). With conversions allowed,
you would not lose Text_IO. I don't know if we'll have time to discuss
this in Denver, but if you are serious about it, by all means get in
touch with your standardization body and let them make a comment. There
is no point in saying "that's how it should have been", and taking no
action to that effect.

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           J-P. Rosen (rosen@adalog.fr)
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