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From: Adrian Hoe <abyhoe@gmail.com>
Newsgroups: comp.lang.ada
Subject: Re: using `use' : what is the best practice ?
Date: Tue, 14 Jun 2011 19:25:03 -0700 (PDT)
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On Jun 7, 11:32=A0pm, milouz <a.micheli...@gmail.com> wrote:
> Hi guys,
> Sorry with my annoying questions, but it's not easy to program in Ada
> after 20 years programming in asm / C ;-)
>
> Maybe a not so anecdotic question : when using the 'use' clause ?
>
> My first thought is that using 'use' is not good because it masks the
> package tree.
> For example, if I have 2 packages with procedures sharing the same
> name, example `P1.Foo' and `P2.Foo', my code won't be very readable if
> I only write the short name (`Foo') :
>
> =A0 =A0with P1; use P1;
> =A0 =A0with P2; use P2;
>
> =A0 =A0procedure Main is
> =A0 =A0 =A0 My_Val : Integer;
> =A0 =A0begin
> =A0 =A0 =A0 Foo(My_Val); =A0-- P1 or P2 ?
> =A0 =A0...

I "use" packages when I need to "use" its type and many calls to
subprograms in it to avoid lengthy code.

You can always explicitly write:

         P1.Foo ( My_Val );
         P2.F00 ( My_Val );

The beauty of Ada is that it is not only an implementation language,
it is also a documentation language.


> But always avoiding 'use' give some rather obfuscated code, especially
> when using some specific arithmetic operator. For example, playing
> with Address arithmetic without 'use' :
>
> =A0 =A0with System;
> =A0 =A0with System.Storage_Elements;
>
> =A0 =A0procedure Main is
> =A0 =A0 =A0 A : System.Address;
> =A0 =A0 =A0 N : Integer;
> =A0 =A0begin
> =A0 =A0 =A0 A :=3D System.Storage_Elements.To_Address(16#10000#);
> =A0 =A0 =A0 N :=3D 4;
>
> System.Storage_Elements."+"(System.Storage_Elements.Storage_Offset(N),
> A);
> =A0 =A0end Main;
>
> The same code with 'use' is more readable :
>
> =A0 =A0with System; use System;
> =A0 =A0with System.Storage_Elements; use System.Storage_Elements;
>
> =A0 =A0procedure Main is
> =A0 =A0 =A0 A : Address;
> =A0 =A0 =A0 N : Integer;
> =A0 =A0begin
> =A0 =A0 =A0 A :=3D To_Address(16#10000#);
> =A0 =A0 =A0 N :=3D 4;
> =A0 =A0 =A0 A :=3D A + Storage_Offset(N);
> =A0 =A0end Main;


with System; use System;
with System.Storage_Elements; use System.Storage_Elements;

procedure Main is
   A : System.Address;
   ...

This will be more readable though, IMO.


--
Adrian Hoe
http://adrianhoe.com/adrianhoe