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Date: 16 Sep 92 05:24:46 GMT
From: munnari.oz.au!yoyo.aarnet.edu.au!huon.itd.adelaide.edu.au!cs.adelaide.edu
.au!andrewd@uunet.uu.net  (Andrew Dunstan)
Subject: Re: Novice Question On Generics
Message-ID: <196geuINNacl@huon.itd.adelaide.edu.au>
List-Id: <comp.lang.ada>

In article <1992Sep15.184345.12197@saifr00.cfsat.honeywell.com>, lam@saifr00.cf
sat.honeywell.com (Josh Lam) writes:
[sorry for long repost - I'v cut it down a fair bit]
|> with Queue                                with Queue
|> package A  is                             package B is 
|>  ...                                      ...
|>  type A_record is                           type B_record is
|>   record                                     record
|>    ...                                         ...
|>   end record                                 end record
|>  package my_QA is new Queue(A_record);       package my_QB is new Queue(B_re
cord);
|>  ...                                          ...
|>  Run_Proc(X : A_record);                      Run_Proc(Y : B_record);
|>  ...                                          ...
|> end A;                                    end B;
|> 
|> Now the Run_Proc procedures for both packages will look like:
|> 
|> Run_Proc(X : A_record) is                 Run_Proc(Y : B_record) is
|> begin                                     begin
|>   my_QA.enqueue(X);                         my_QB.enqueue(Y);
|> end Run_Proc;                              end Run_Proc;
|> 
|> Basically, they contain the same functionality.  In this example, I only
|> wrote one line of code for simplicity of illustration, in reality, there
|> could be more lines of code but same functionality.  The only difference
|> is the queue instantiations my_QA and my_QB.  
|> 
|> Question:
|> Is there a way to write a generic procedure Run_Proc that the two packages 
|> A and B can use?   Note that the user *does not* need to know my_QA 
|> and my_QB ie they are private members to A and B respectively and Run_Proc i
s 
|> the only interface to the outside world. ie, The user only need to type 
|> A.Run_Proc(X) or B.Run_Proc(Y).


I think this is what you want:

with queue;
generic
   type x is private;
package run_proc_pack is
   -- following line might be in the body, if queue not needed to be public
   package rpq is new queue(x);
   procedure run_proc(a : x);
end run_proc_pack;
package body run_proc_pack is
   procedure run_proc(a: x) is
   begin
      rpq.enqueue(a);
   end run_proc;
end run_proc_pack;

...

package a_run is new run_proc_pack(a_record);
package b_run is new run_proc_pack(b_record);

...

a_run.run_proc(a_rec);
...


without knowing more about what you are actually trying to do, it is
hard to tell if this is what you really want.


-- 
#######################################################################
#  Andrew Dunstan                   #   There's nothing good or bad   #
#  Department of Computer Science   #   but thinking makes it so.     #
#  University of Adelaide           #                                 #
#  South Australia                  #          - Shakespeare          #
#  net: andrewd@cs.adelaide.edu.au  #                                 #
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