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Subject: Re: Your wish list for Ada 202X
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Date: 2014-04-23T17:48:47-06:00
List-Id: <comp.lang.ada>

On 23-Apr-14 16:00, J-P. Rosen wrote:
>
> Actually, the carefull separation between "with" and "use" has been
> designed to allow opening visibility just when and where you need
> access to the content. Putting "use" on top of the unit defeats the
> very purpose of the "use" clause.

I'm going to disagree, slightly; putting a use clause at the top of the 
unit can certainly be valid -- consider using a thick-binding hierarchy, 
to a library that you're using to implement functionality X -- since 
your writing to that binding it is perfectly valid to USE it. (And since 
you're writing specifically to that binding there's little sense in not 
doing it -- though, to be fair, you can make it so that the structure of 
your application is independent of the library via a "layered" 
approach... then using a different lib is simply writing to the 
application/binding interface you already have.)

Another reason is uniformity -- if you have a unit that's going to be 
using a lot of the operations from different units you can use them all 
and keep things uniform:

With
Ada.Integer_IO,
Ada.Text_IO,
Some_Lib.Text_IO,
Some_Lib.Types;

Use
Ada.Integer_IO,
Ada.Text_IO,
Some_Lib.Text_IO;

-- Library-Level Put
Procedure Put( Input : Some_Lib.Types.Some_Record ) si
begin
   Put( "Integer-Field:" );
   Put( Input.Integer_Field );
   New_Line;
   Put( "Name:" );
   Put( Input.Name );
   New_Line;
   --... and so on.
end Library_Level_Put;

> "use" clauses are very helpful and make code a lot more readable,
> provided they are restricted to the innermost context where they are
> useful (and of course, you have an AdaControl rule to enforce that ;-) ).

I fully agree that they are useful/helpful.