Re: Exclusive file access

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On Mon, 07 Sep 2015 20:27:58 +0200, Florian Weimer wrote:

> * Dmitry A. Kazakov:
> 
>> Anything you can encode in Unicode you can encode in Unicode.
> 
> This is simply not true across multiple Unicode versions (and when
> dealing with multi-byte encodings).

Versions of Unicode are irrelevant.

> It is not possible to express all
> possible UCS-2 sequences in UTF-32, in the sense that converting from
> UTF-32 completely covers the entire set of UCS-2 strings.

You can represent all code ranges in UTF-32. I don't think the language
should care about "visible characters." This insanity can be safely
ignored.
 
>>> The user may select a file, but the application cannot open it.
>>> That's a poor user experience.
>>
>> That is not a problem at all. You cannot create a 999TB large file either.
> 
> Well ...
> 
> -rw-r--r-- 1 fw fw 1098412116148224 Sep  7 20:23 t
> 
> And I expect that I can delete it, too.  Anything else would be a bug.

Bug of the OS or of your program?

Ada.Text_IO could also tell you that the file was created and then proclaim
anything else a bug.

>> System-specific constraints put on an implementation do not effect the
>> interface, which has Name_Error in it already.
> 
> It's not a constraint that the system imposes, it's something that
> requires careful thought from the programming language implementor.

You cannot have files named ".." on some OSes. That has nothing to do with
Ada or any other language.

> If they impose stronger constraints on strings than what the file
> system enforces, you end up with non-nameable files and a poor user
> experience.

That is the problem with current Ada.Directories and Ada.Text_IO. Not
because of a constraint, but because the constraint is meaningless in a
system that allows wider sets of characters than ASCII.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de