Re: 3-bit array ...

[Robert A Duff <bobduff@world.std.com>]

Nick Roberts <nickroberts@callnetuk.com> writes:

> Just out of curiosity ... what is a 3-bit array?

People are using that to refer to a packed array of 3-bit components.
For example:

    type T1 is range 1..5;
    type T2 is array(Integer range <>) of T1;
    pragma Pack(T2);

In Ada 95, T1'Size = 3 -- a statement that will no doubt elicit the
usual complaints from Robert Dewar about loose-cannon language design
teams run amok.  ;-) ;-)

Also in Ada 95, T2'Component_Size will be either 3 or 4, depending on
the whim of the compiler writer, which doesn't seem like a good language
design decision.  I'm assuming a 32-bit machine, here.  GNAT has always
supported packing to the 3-bit level.  AverStar's front end, and the
Green Hills compiler that uses AverStar's FE, used to use 4, but now
uses 3, due to customer demand for it.  That's what this whole
discussion has been about.

There's also the issue of whether you can say:

    for T2'Component_Size use 3;

instead of the pragma Pack above.

- Bob