Re: Ada exception block does NOT work?

["Frank J. Lhota" <NOSPAM.FrankLho@rcn.com>]

"Robert A Duff" <bobduff@shell01.TheWorld.com> wrote in message 
news:wccslx4gumc.fsf@shell01.TheWorld.com...
> ...
> To me, "pointer" does not imply "a single machine address".
> To me, "pointer" means something that can point at things,
> and that includes fat pointers, pointers containing array
> dope, pointers represented as offsets instead of addresses,
> double indirections, &c.

Thats fine, but also understand that to many others, "pointer" does mean "a 
single machine address". It certainly does not hurt to introduce a new term 
to avoid potential misunderstandings.

> To me, "pointer" and "reference" are synonymous.

OK, but just be aware that in C++, "pointer" and "reference" are not 
synonyms.

> And "address" or "machine address" can be used for the hardware-level
> concept.
>
> An index into an array can be used as a pointer to a particular
> array element.

So the number 3 can be thought of as a pointer into any array indexed by a 
integer. An interesting concept, but this is certainly a non-standard use of 
the term "pointer".

> Ada evolved from Pascal, and Pascal called them pointers.
> In Pascal, there was no requirement or implication that
> they must be a single machine address.  There is no need
> for array dope in Pascal, but adding array dope doesn't seem
> like it requires renaming the whole concept.

For the record, I know of no Pascal compiler that implements a pointer as 
anything other than a machine address.

>> As for Integer, you're quite right, but it's also quite natural to use
>> that name (or a shortened form of it) for such a subset. Such a usage is
>> quite common in computer languages; see FORTRAN (1955?) for an
>> example. What would be a better name for such a type?
>
> I'd use "Integer" for what Lisp calls "bignums" -- integers that can
> grow without bound (except of course you can run out of memory,
> but that's true of Strings and whatnot, too.  I'd call the integer type
> that is based on the hardware (e.g. 32-bit integers) "Machine_Integer".
> And I wouldn't put it in a package called "Standard" and I wouldn't
> make it automatically visible everywhere.
>
> I think one ought to be allowed to say:
>
>    type T is range 1..10**100;
>
> Portably.

Now that is an interesting concept. I am fond of divorcing the language from 
platform constrains when practical. There are, however, some practical 
concerns about this proposal. An Ada 'bignum' type would undoubtedly be a 
controlled type, introducing more overhead than one would expect in a scalar 
type.

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