Re: Why no Ada.Wide_Directories?

["Peter C. Chapin" <PChapin@vtc.vsc.edu>]

On 2011-10-15 10:47, Dmitry A. Kazakov wrote:

> And it is just silly to make the point that Ada programs should read/write
> only files created by other Ada programs [compiled by the same compiler, I
> guess].

It's not that silly.

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. 
Such is the nature of a standard. Thus the standard model of "file" and 
"file system" will be a simplified abstraction of the real thing on any 
particular system. A portable program can only make use of that 
simplified abstraction if it expects to remain portable.

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.

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

I can appreciate that accessing files with Unicode names might be a 
useful thing to do in a standard program. What happens when such a 
program tries to create files with such names on a system that doesn't 
support them? I suppose a solution could be found, but I can also see 
how it would get ugly.

Peter