Re: using `use' : what is the best practice ?

[Adrian Hoe <abyhoe@gmail.com>]

On Jun 7, 11:32 pm, 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') :
>
>    with P1; use P1;
>    with P2; use P2;
>
>    procedure Main is
>       My_Val : Integer;
>    begin
>       Foo(My_Val);  -- P1 or P2 ?
>    ...

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' :
>
>    with System;
>    with System.Storage_Elements;
>
>    procedure Main is
>       A : System.Address;
>       N : Integer;
>    begin
>       A := System.Storage_Elements.To_Address(16#10000#);
>       N := 4;
>
> System.Storage_Elements."+"(System.Storage_Elements.Storage_Offset(N),
> A);
>    end Main;
>
> The same code with 'use' is more readable :
>
>    with System; use System;
>    with System.Storage_Elements; use System.Storage_Elements;
>
>    procedure Main is
>       A : Address;
>       N : Integer;
>    begin
>       A := To_Address(16#10000#);
>       N := 4;
>       A := A + Storage_Offset(N);
>    end 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