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From: Maciej Sobczak <see.my.homepage@gmail.com>
Newsgroups: comp.lang.ada
Subject: Design - cyclic dependencies
Date: Fri, 26 Oct 2007 05:26:00 -0700
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Date: 2007-10-26T05:26:00-07:00
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Consider:

--  a.ads:
package A is
   type T is new Integer;
   procedure P;
end A;

--  a.adb:
with B;
package body A is
   procedure P is
      X : T;
   begin
      B.P (X);
   end P;
end A;

--  b.ads:
with A;
package B is
   procedure P (X : A.T);
end B;

--  b.adb:
package body B is
   procedure P (X : A.T) is
   begin
      null;
   end P;
end B;

There are two logical modules A and B, implemented as packages.
There is no cyclic dependency between the specifications of these
packages and the code is legal.
Still, there is a design-level cyclic dependency between the whole
modules in the sense that A depends on B (A calls some operation of B)
and that B depends on A (B uses some type from A).

Being legal does not imply being good and therefore I ask: do you
consider this kind of design-level cyclic dependency to be acceptable?
If not, what measures would you recommend to correct it?
Extracting T to another package is probably the only reasonable
option, but then there are variants of it (child or sibling package,
etc.).

--
Maciej Sobczak * www.msobczak.com * www.inspirel.com