Re: Mut. Recurs. in Ada9X w/o Breaking Encaps.?

[Magnus.Kempe@di.epfl.ch (Magnus Kempe)]

stt@spock.camb.inmet.com (Tucker Taft) writes:
: 
: The type conversion toward the end of your example is
: illegal (at least according to *our* Ada 9X front end ;-).

Damn.  Thanks.  Here's a fix, which is also accepted by GNAT :-)
Is your Ada 9X front end a program, or a human?

private
package Company.Offices.Ptrs is
  function Ptr (The_Office : Office_Reference)
    return Office_Pointer;
end Company.Offices.Ptrs;

package body Company.Offices.Ptrs is
  function Ptr (The_Office : Office_Reference)
    return Office_Pointer is
  begin
    -- here we "see" that Office is derived from Office_Parent
    return Office_Pointer (The_Office);
  end Ptr;
end Company.Offices.Ptrs;

with Company.Employees.Ptrs;
with Company.Offices.Ptrs;
package body Company.Common is
  function Office_Occupied_By (The_Employee : in Employees.Employee)
    return Offices.Office_Pointer is
  begin
    return Offices.Ptrs.Ptr (Employees.Ptrs.Office_of (The_Employee));
  end Office_Occupied_By;
  ...
end Company.Common;

: In any case, to me it is much simpler to declare abstract
: versions of Employee and Office in the same package, with appropriately
: mutually recursive (abstract) operations declared there as well.

I agree, but John Volan wanted something else...  My solution completely
avoids showing abstract and/or class-wide stuff to the client.

-- 
Magnus Kempe		"I know not what course others may take, but as for me,
Magnus.Kempe@di.epfl.ch  Give me Liberty... or give me Death!" -- Patrick Henry