Re: Dimensionality Checking (Ada 20XX)

["Mark Lundquist" <no.spam@getalife.com>]

Hi Nick, I still have yet to get around to a full reply to this, so I
thought I'd take a whack at the easy bits :-)

"Nick Roberts" <nickroberts@adaos.worldonline.co.uk> wrote in message
news:9v37rs$cdmva$1@ID-25716.news.dfncis.de...
> Sorry not to reply to this in full sooner.
>
> "Mark Lundquist" <mlundquist2@attbi.com> wrote in message
> news:haTQ7.21816$wL4.49551@rwcrnsc51...
>
>
> > > There's the question of private types. I feel that the requisite
> > conversions
> > > and other mixed operations should be provided for a private type
> > explicitly
> > > (in its package spec), and that these operations should do the
requisite
> > > conversion and checking, which may well be more complicated than mere
> > > scaling and dimensionality. The unit facilities would, of course, be
> > > applicable to those components which were of unit-specific
(fixed-point)
> > > types.
> >
> > I'm not sure quite what you're getting at there, but it sounds like it
> might
> > be related to an issue I've been thinking about, which is that these
units
> > currently would not be able to work with "quasi-numeric" abstractions
such
> > as people define for things like rational numbers, infinite-precision
> > arithmetic, etc.
> > ...
>
> Correct. (The example presented to me was Ada.Calendar.Time).

There you go... Calendar.Time is a perfect example.

> > 1) You have to be able to handle logarithmic units... that's easy, for a
> > unit U:
> >
> >     U'Log (B)    -- denotes the log to the base B of U
> >     U'Exp (B)    -- denotes B to the power U
>
> Or alternatively, sticking closer to my design, the package Ada.Units
could
> have functions Log and Exp. This presumably means that the dimensions of a
> unit could be non-integral?

No, you're holding your exponetiator backwards... here, like *this*...
that's more like it :-)
Non-integer exponents signify roots, not log/exp.

Cheers,
Mark

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