Re: Flags in Ada?

[tmoran@bix.com]

>Most of the techniques that have been proposed for this use packed
>boolean and representation specs within the visibile part of the
>package spec.  My experience is that this can be a dangerous approach,
>particularly for portability.
>
  ...
> package POSIX is
>  ...
>    type Option_Set is private;

Where is the conceptual focus?  If the important object is the set of
flags (Option_Set here), then certainly it should be dealt with as an
entity - either hiding the implementation details as per your example
or exposing it as an array of booleans (packed if interfacing or
other reasons so indicate).  But if the 'flags' are in fact logically
heterogenous data, that just happen to be tossed together to match
some external interface, then, like all heterogeneous data, they should
be in a record, not an array.  If it's just an interfacing requirement
that names and places the bits, it seems to me that like all system
dependencies their specification should be buried inside a package which
exports a clean, logical, and portable view of their relevant information.