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From: Georg Bauhaus <bauhaus@futureapps.invalid>
Newsgroups: comp.lang.ada
Subject: Re: Running a preprocessor from GPS?
Date: Sat, 01 Aug 2015 22:30:48 +0200
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Xref: number.nntp.giganews.com comp.lang.ada:194614
Date: 2015-08-01T22:30:48+02:00
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On 01.08.15 20:15, Paul Rubin wrote:
> "Jeffrey R. Carter" <spam.jrcarter.not@spam.not.acm.org> writes:
>> The pkg is a very important concept in Ada, and your insistence that there has
>> to be a Get_Instance function shows that you don't fully understand it yet.
>> Until you do, you won't really understand Ada.
>
> Is there a good place to read about this?  I had the impression that
> package initialization runs unconditionally.  EGarrulo was asking how to
> get it to run only in response to a runtime request that might never
> happen.


I'm sneaking this in here. A generic instance has context, sometimes
non-static context, on which it depends:

with Ada.Text_IO;
with Ada.Calendar;  use Ada.Calendar;

procedure Late is
    
    Start : Time;
    
    generic
       Now : Time;
    package Again is
       --  tells the time
    end Again;
    
    package body Again is
    begin
       Ada.Text_IO.Put_Line (Duration'Image (Now - Start));
    end Again;
    
begin
    Start := Clock;
    loop
       delay 1.0;
       declare
          package Tick is new Again (Now => Clock);
       begin
          null;
       end;
    end loop;
end Late;