Re: Usage of Interfaces with Ada 95

["Robert I. Eachus" <rieachus@comcast.net>]

Hyman Rosen wrote:

> Let me see if I have this right. I believe that in Ada, controlled
> types can be declared only at library level, correct? So if the
> mix-in is going to do something with its containing object, then
> doesn't the type of the containing object have to be declared at
> library level as well? This means that the awkward inheritance-based
> model of controlled drives the package structure, which seems like a
> bad idea to me.

There are only two times I tend to put type declarations inside 
procedures:  In small examples where it is nice to be able to tell 
someone to compile a file and run it, and when the main procedure is a 
manager for a complex application, and I need to enumerate the parts:
type Pass is (Syntax_Analysis, Semantic_Analysis, Optimizer, 
Code_Generation);

So other than trivial examples, ALL tagged types I create are at the 
library level.  It doesn't matter if the package containing the is 
nested six deep within other packages, as long as the outermost package 
is at the library level, all the nested packages are also.

-- 
                                                     Robert I. Eachus

"Quality is the Buddha. Quality is scientific reality. Quality is the 
goal of Art. It remains to work these concepts into a practical, 
down-to-earth context, and for this there is nothing more practical or 
down-to-earth than what I have been talking about all along...the repair 
of an old motorcycle."  -- from Zen and the Art of Motorcycle 
Maintenance by Robert Pirsig