Re: Separate Compilation in Programming Languages

[Ray Blaak <rAYblaaK@STRIPCAPStelus.net>]

<adaworks@sbcglobal.net> writes:
> But, in Ada we can defer the dependency to the package body.  In Java you
> cannot defer that dependency.  A dependent unit, when the specification
> changes is combined with its implementation.  Therefore, every dependent
> specification must also be compiled.  As noted below, we can defer the
> dependency in Ada to the package body.  There is nothing analogous to this
> in Java.

This is simply false.

I am starting to think that *I* don't have the sufficient communication
skills. There is a fundamental disconnect here.

Consider this Ada situation:

  Client C ------> Package P spec
                     |
                     |
                   P body

When P's spec changes, both C and P's body need to be recompiled.

When only P's body changes, C is unaffected.

Consider this Java situation:

  Client C ------> interface P_Spec
                     |
                     |
                   class P_Body implements P

When P_Spec changes, both C and P_Body need to be recompiled.

When only P_Body changes, C is unaffected, P_Spec is unaffected.

I don't know how else to say it more clearly.

Note that if anyone is referring to P_Body then they will be affected, but the
idea is that one takes the care so the clients only use P_Spec. This takes
effort and discipline, making things less convenient than Ada, but the ability
to have the separation is there in the Java language.

> Perhaps.  But I still don't see how one can defer the dependency of a
> Java signature to the implementation of the Java class and prevent
> the need for recompiling the entire architecture when the signature of
> a parent class changes.   

Maybe the disconnect is here. Are you talking about how spec changes ripple
down, or are you talking about how body changes ripple down? Spec changes
affect clients and bodies, both in Java in Ada. Body (implementation) do not
affect clients that only refer to the spec, both in Java and Ada.

-- 
Cheers,                                        The Rhythm is around me,
                                               The Rhythm has control.
Ray Blaak                                      The Rhythm is inside me,
rAYblaaK@STRIPCAPStelus.net                    The Rhythm has my soul.