RE: [Ada-Comment] Extensible Enumerated Types

["Robert C. Leif, Ph.D." <rleif@rleif.com>]

From: Bob Leif
To: Pascal Leroy et al.
I have taken the liberty of cross-posting my reply to Comp.Lang.Ada, which
is where the previous discussion occurred. You wrote, "I encourage you to
write a detailed proposal on how this would be integrated with the rest of
the language, and how it could be implemented."

I did not see a requirement that in order to propose an extension to Ada one
must be an expert in Ada compilers. In fact in some cases, it may be that
such expertise could even be detrimental. As I have repeatedly stated, there
are both technology driven and market driven aspects to product development.
In my own field of Analytical Cytology (Biomedical Engineering), I would
never limit customer or marketing suggestions to only those that the
individual who made the proposal actually knew how to do the implementation.
In fact one major reason for selecting one of the 3 proposed implementations
is: How easy would it be to teach in a first year computer science course? I
might note that my suggestion came from the problem of implementing a
software package.


-----Original Message-----
From: Pascal Leroy [mailto:pleroy@rational.com]
Sent: Tuesday, February 13, 2001 2:34 PM
To: rleif@rleif.com
Cc: Ada-Comment List
Subject: Re: [Ada-Comment] Extensible Enumerated Types


> Topic: Extensible Enumerated Types
>
> type Prefix_Type is (None, Mr, Ms, Miss, Mrs, Dr, Prof, Rev, Other);
>
> (1)
> supertype Army_Prefix_Type is (Prefix_Type, Private, Corporal, Sergeant,
> Lieutenant, Captain, Major, Colonel, General);
>
> (2)
> type Army_Prefix_Type is new Prefix_Type with (Private, Corporal,
Sergeant,
> Lieutenant, Captain, Major, Colonel, General);
>
> (3)
> type Army_Prefix_Type is (Prefix_Type�range & ((Private, Corporal,
Sergeant,
> Lieutenant, Captain, Major, Colonel, General));

Extensible enumeration types are certainly an interesting idea.  In fact at
some point during the 9X process they were part of the Mapping Document, and
got trimmed.  I think Tuck mentioned them again during the last ARG meeting.

But if you feel that this feature should be added to the language, I
encourage you to write a detailed proposal on how this would be integrated
with the rest of the language, and how it could be implemented.  Coming up
with syntax is very easy (I have no doubt that the "right" syntax is #2,
btw) but that's only about 1% of the work.  I think that the ARG would be
much more interested in looking at this idea if there were a real proposal
on the table, rather than a one-line example of the syntax.

If we had a real proposal, it would also be possible to evaluate the
implementation complexity and balance that with the potential benefits.

If you are interested in writing such a proposal, just send it to
Ada-Comment and it will be given due consideration.

Pascal