Re: Classes vs types; what's the difference?

Re: Classes vs types; what's the difference?

[Michael Feldman]

In article <1993Apr12.150148.9736@evb.com> jgg@evb.com (John Goodsen) writes:
>
>I still maintain that the "better marketing" argument for using
>"class types" instead of "tagged types" in Ada 9X has been to this
>point unchallenged...
>
I think I'm tending to agree with this (how's that for hedging my bets?).
Nothing would change syntactically by substituting "class" for "tagged".
One new reserved word is required in either case; "tagged" is used nowhere
else in the language, and neither is "class" _as a reserved word_.
(T'Class is used as an attribute, but Ada seems to have no problems
overloading an attribute with a reserved word, as 'Range illustrates).

Semantically, "class type" would logically connote "a type that can give
rise to a class, which is precisely what a tagged type is; T'Class in a 
declaration then refers to T and anything in the derivation tree rooted at T, 
so it all seems consistent.

It seems, then, that a simple substitution of the new reserved word CLASS
for the (equally new reserved word) TAGGED would do the trick, and if it 
would help the marketing while hurting nothing else, it seems to me that 
we have a non-problem here.

Have I missed something critical? Other than a certain stubborn commitment 
to the word "tagged", what's wrong with this?

Mike Feldman

Re: Classes vs types; what's the difference?

[Charles Lindsey]

In <1993Apr12.152305.10571@seas.gwu.edu> mfeldman@seas.gwu.edu (Michael Feldman
) writes:

>In article <1993Apr12.150148.9736@evb.com> jgg@evb.com (John Goodsen) writes:
>>
>>I still maintain that the "better marketing" argument for using
>>"class types" instead of "tagged types" in Ada 9X has been to this
>>point unchallenged...
>>
>I think I'm tending to agree with this (how's that for hedging my bets?).
>Nothing would change syntactically by substituting "class" for "tagged".
>One new reserved word is required in either case; .

Can I remind you that I proposed the reserved word "classified" for this
purpose some while back. It has a few, but helpful, advantages.
	1) It is an adjective.
	2) It implies that the thing is not quite a genuine class, as
	understood elsewhere, but is clearly related.
	3) It carries a feeling that something special has been done to
	values of that type (such as adding a tag, or 'classification') to
	them, without actually ramming the idea down your throat as "tagged"
	does.



-- 
Charles H. Lindsey ------------------------------------------------------------
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Re: Classes vs types; what's the difference?

[Wes Groleau X7574]

In article <1993Apr15.093550@lglsun.epfl.ch> magnus@lglsun.epfl.ch (Magnus Kemp
e) writes:
>So, there are good reasons not to go the "class type" way.
>Finding other reasons is left as an exercise for the readers...

Like readability, as in making it similar to a human language, and making it
somewhat descriptive of what's happening.

   type roster is class record .....  :-)

Re: Classes vs types; what's the difference?

[cis.ohio-state.edu!zaphod.mps.ohio-state.edu!cs.utexas.edu!csc.ti.com!til]

In article <C5HGHA.9Jq@clw.cs.man.ac.uk> chl@clw.cs.man.ac.uk (Charles Lindsey)
 writes:

>Can I remind you that I proposed the reserved word "classified" for this
>purpose some while back. It has a few, but helpful, advantages.

That is probably not a good choice of a reserved word for a language that is
going to be used in DoD applications.  "Classified" has a VERY well-known and
VERY long-established meaning in that arena.