Re: Why no Ada.Wide_Directories?

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

On Sun, 16 Oct 2011 20:15:11 -0400, Peter C. Chapin wrote:

> In order to talk sensibly about files the standard needs to define a 
> model of "file" and, in this case even "file system." This needs to be a 
> model that will be applicable to the widest range of platforms possible. 

Right

> Such is the nature of a standard.

Thank you for making my point. The standard disregards the above principle
by using Latin-1 encoding for file names. 

> Thus the standard model of "file" and 
> "file system" will be a simplified abstraction of the real thing on any 
> particular system.

"Simplified" is in contradiction with "widest range". In order to support
widest range it must generalized, abstracted, rather than simplified,
degraded.

Ada adopted Unicode. Unicode is a generalized model capable to handle any
encoding the target platform might use. The programmer need not to know the
actual encoding, it becomes irrelevant.

> If other files on the system also conform to that simplified model, that 
> is good. A portable program will be able to manipulate them. However, if 
> a program wishes to manipulate all files on a particular system, with 
> their full generality, system-specific techniques are going to be necessary.

Wrong. All file systems share common features, which can and must be
properly abstracted. System-specific are the implementations, not the
package specifications.

> For example, I don't believe the Ada standard allows one to access 
> information about a file's owner.

This has nothing to do with file names, but if the standard wished to
address access rights, it could do it as well.

> Yet every file on my Linux system has 
> an owner. If I want to write a portable Ada program I have to live 
> without that information. If the Ada standard goes on to say that I 
> can't access files with names containing "exotic" characters, how is 
> that any different in principle?

Because inability to spell the file name is not same as lacking access
rights. Access rights are external to the program code. The file name,
coded as a string literal is a part of the program. Failure of the former
is not a bug. The latter is a bug, because the file exists, is accessible
and has proper name. A program bug which cannot be fixed is a language
design bug.

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