Re: Ada OOP alternatives?

[Georg Bauhaus <rm.dash-bauhaus@futureapps.de>]

Dmitry A. Kazakov schrieb:
> On Fri, 25 Jul 2008 10:47:49 +0200, Georg Bauhaus wrote:
> 
> [...] 
>> Suppose you try to use an IDE in place of "separate",
>> to hide away the details of Special_Case. Then the dependences
>> on the with'ed package Ada.Text_IO and on All_Kinds_of_Things_Neccessary
>> will have to be listed for the entire package.
> 
> Yes, but it would not change dependencies.

Yes, separate units can change the dependences of a package
body. E.g., in a good many cases, a package body can be compiled
without the separate unit. (It can be compiled without
a child package, too).

When the separate unit depends on a yet-to-be written/delivered
package, the parent body is not affected.  You cannot achieve this
kind of compilation advantage when you put the separate subprogram
into the parent body instead. (Not different from a child.)


> Better, there should be a "without" clause/pragma (:-))

:-)


> So, yes, an ADT, even if it is a singleton today.

For what?  I think that language theorists have ways to
associate a synthetic OO type with a singleton package
without loss.


>  Only objects should have states.

Yes, only objects can have states. I am assuming you mean that every
variable object of a scope other than the scope of an innermost
subprogram is evilly global?


> Global variables is
> a no-no. There cannot be stateful procedures otherwise than impure, with
> global variables.

When the "global" variable cannot be manipulated by
anything besides a visible procedure, this statement
is false.

private
package Parent.Singleton is
    procedure Bump(Item: Some_Type);
end;


I see you disagree with state variables hidden in singleton package
bodies. I claim that passing them around instead has potential for
creating spaghetti. Plus it requires a visible, private type
and a way to enforce only one object.

The weekend is near, I'll go for a walk if you don't mind.


--
Georg Bauhaus
Y A Time Drain  http://www.9toX.de