RE: [Ada-Comment] Extensible Enumerated Types

RE: [Ada-Comment] Extensible Enumerated Types

[Robert C. Leif, Ph.D.]

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

Re: [Ada-Comment] Extensible Enumerated Types

[Marc A. Criley]

"Robert C. Leif, Ph.D." wrote:
> 
> 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.

Bob,

Relax.

Adding extensible enumerated types to Ada would be a non-trivial
addition to the language.  What Pascal is requesting (and I don't think
it's out-of-line) is a starting point for discussion.  If a proposal for
a language modification made to the ARG is accompanied by an analysis of
how the feature would behave in a variety of circumstances, and how it
might impact related features, it gives everyone a headstart on
conceptualizing and evaluation.  As neither your nor I are language
lawyers, we certainly are not expected to provide a comprehensive,
end-to-end proposal regarding the addition.

By having spent some time evaluating what the impact of the new feature
would be, along with the concept of how it should act, the ARG can start
looking at the various aspects of the feature that have been initially
covered in the proposal, rather than having to uncover each such aspect
themselves.

Marc A. Criley
Senior Staff Engineer
Quadrus Corporation
www.quadruscorp.com


> 
> -----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

RE: [Ada-Comment] Extensible Enumerated Types

[Robert C. Leif, Ph.D.]

From: Bob Leif
To:Randy Brukardt et al.
Randy, many thanks for solving the mystery. Since this discussion was
originally on Comp.Lang.Ada and others may have been searching for this
text, I have taken the liberty of posting it.
---------------------------------------------------------------
SNIP
I went and looking in a dusty carton in the far corner of the
basement of our office, and looked at all of the old mapping documents.

The proposal disappeared between Mapping 2.0 (May 1991) and Mapping 3.0
(June 1991). These versions probably were internal use only (my copy of
Mapping 2.0 was faxed me from AETECH), so I doubt Dr. Leif could find it
anywhere.

So, here is the complete proposal (so far as I can find) from Mapping 2.0:

3.5.1 Enumeration Types

An enumeration type may be extended as part of a type derivation by
specifying additional enumeration literals. The enumeration literals for the
type include those corresponding to the parent and the new enumeration
literals. For each enumeration literal of the parent, there is a
corresponding literal for the new type (with the corresponding position and
ordering). The position number of the first enumeration literal in the
extension part is one more than the position number of the last enumeration
literal of the parent type.

Examples:

    type Boolean_with_Unknown is new Boolean with (Unknown);
       -- Boolean_with_Unknown has three enumeration literals,
       -- False, True, and Unknown with position numbers 0, 1, and 2.

    type Rainbow is (Red, Orange, Yellow, Green, Blue, Indigo, Violet);
    type Full_Color is new Rainbow with (Brown, Black, White);
	 -- Full_Color is an enumeration type with the literals:
       -- Red, Orange, Yellow, Green, Blue,
       -- Indigo, Violet, Brown, Black, White

SNIP

Anyway, enjoy. :-)

			Randy Brukardt.

Re: [Ada-Comment] Extensible Enumerated Types

[Mario Amado Alves]

A provisional implementation is to make

  type T is {A, B, C};
  type Extended_T is new T with {X, Y, Z};

merely syntactic sugar for

  type T is {A, B, C}
  type Extended_T is {A, B, C, X, Y, Z};

Of course there is no proper derivation here. Nevertheless it seems like a
useful construct. I often miss it.

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