Re: Disallowing Pre-Defined Operations

[Robert Dewar <dewar@gnat.com>]

In article <38D9A2E8.F720768@erols.com>,
  whitaker@erols.com wrote:
> No one asks for built-in units checking.  (Actually I did and
several
> others have talked to me about it, but apparently not to ACT.)
This may
> not be unexpected.  ACT talks to the computer people in a
company.
> Computer scientists have no brief for units, they deal with
bits, and
> maybe GUIs.  They get an algorithm and are supposed to
implement it.

Well I can't speak for other vendors, but the above is not
anything like recognizable in terms of our customers and
how we interact and whom we talk to. We definitely talk to
the designers at the top level. It is simply that this
requirement has never arisen.

In wake of the publicity of the Mars mission, even though this
was not a language issue per se, you would think that if anyone
was interested in this issue, it would have come up now.

Note that the derived types in Ada go quite far in the direction
of avoiding junk unintentional mixing of units.

What would be interesting is to gather a catalog of instances
in which units problems *preventable by the kind of feature
being discussed here* have actually occurred and caused trouble.

I see a lot of people hypothesizing that this would be a useful
feature that would sell Ada, but as we all know in CLA, there
is that kind of support for almost any imaginable feature in
Ada. What would be more interesting is specific war stories that
we could analyze to see how an additional feature might have
helped.

Robert Dewar
Ada Core Technologies




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