Re: Instanciation in a package spec.

[Robert A Duff <bobduff@shell01.TheWorld.com>]

Dmitry A. Kazakov <mailbox@dmitry-kazakov.de> writes:

> >The problem here is the elaboration model of Ada.  The *visibility* of
> >things is too closely tied to the *elaboration* order.  I have worked
> >out a different model of elaboration that doesn't have this problem (but
> >still retains all the advantages of the Ada model).  Unfortunately, it's
> >not Ada.
> 
> Why it cannot become Ada?

My model would require incompatible changes to Ada.
Therefore, it would be suitable for a from-scratch language design,
but it is not suitable for a modification to Ada as it stands today.

> In other words, what is the price of your model?
> 
> Can  X become static (in your model), when F is pure?

Well, I have ideas along those lines, but I think that's a separate
issue.  It depends exactly how "pure" is defined.  Are you willing to
tolerate pure functions with infinite loops?  So the compiler will go
into an infinite loop evaluating a call to F at compile time?
Sounds OK to me, but it might surprise some folks.

Ada currently has no pragma Pure for individual functions.  Just
packages.

Ada currently allows machine-code inserts in pure code.  Must the
compiler have access to the target machine during compilation?
Is it even meaningful?

- Bob