Re: with use - again [Was: Manifesto against Vector]

[Manuel Collado <m.collado@lml.ls.fi.upm.es>]

Martin Krischik wrote:

> Russ wrote:
> ...
>  
> 
>>with/use Ada.Integer_Text_IO;>
> 
>>is cleaner and simpler than
>>
>>with Ada.Integer_Text_IO; use Ada.Inteqer_Text_IO
> 
> 
> You know that this has cost me when I first read Ada Tutorials and tried to
> understand what what was going on. Every package was "use"d and I was
> wondering: And where is this function, procedure, exception coming from?
> 
> The use of "use" should be forbidden in tutorials.
> 
> 
>>And I also that it is a trivial matter to parse the former to produce
>>the latter. I could do it myself in a few minutes. Nor does it break
>>compatibility with legacy code in any way. I see absolutely no
>>reasonable objection to "with/use" (but I have a funny feeling that I
>>may soon be bombarded with a lot of unreasonable objections).
> 
> 
> Why unreasonable? "use" make reading code harder. "package IIO renames 
> Ada.Inteqer_Text_IO" is far better on the reading side. 
> ...

Perhaps the 'use' clause could be made selective, as in the IMPORT 
clauses of Modula-2:

         Modula-2

   (1)  IMPORT module;                          (same as 'with module;')
   (2)  FROM module IMPORT name1, name2, ...;   (selective visibility)
   (3)  FROM module IMPORT ...everything...;    (everything visible)

The equivalent Ada clauses would be:

         Ada

   (1)  with module
   (2)  with module; ...  use module (name1, name2, ...);   (non Ada yet)
   (3)  with module; ...  use module;

Perhaps the form (2) of the 'use' could be an useful addition to the Ada 
language, and it wouldn't break any existing code.

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