Re: Two ideas for the next Ada standard

[dewar@cs.nyu.edu (Robert Dewar)]

T.E.D. asked, replying to me:

"> Two things we have considered adding as options to GNAT, which are not
> extensions, merely source representation issues, are to allow the
> private part to appear in a separate file, or to allow it to appear
> in the body.

Wouldn't that make package bodies dependant on the BODIES of every package
that they "with" (even indirectly)? It seems like that could really balloon
compilation times. How would the inevitable circular dependancies be handled?"

Well you are dependent on bodies anyway if there is any inlining or any
generic subprograms.

The GNAT sourced based model COMPLETELY eliminates the problems of circular
dependencies. That's something important that you have missed. 

Indeed one of the big advantages of GNAT is that inline dependencies do not
have this problem.

Consider:

  package A with's B, and inlines from it
  package B with's A, and inlines from it

In a traditional library model you can only get inlining in one direction,
depending on the order of compilation. With the GNAT sourced based approach,
you get inlining in both directions, regardless of the order of the
compilation.

Dependencies can never be circular, because in GNAT, dependencies are of
objects on sources, not, as in a library model, of units on other units.