Re: Zoo question

[Ted Dennison <dennison@escmail.orl.mmc.com>]

Bob Gilbert wrote:
> 
> In article <320F16B6.6944@lmtas.lmco.com>, Ken Garlington <garlingtonke@lmtas.lmco.com> writes:
> > Here's a little brain teaser we received recently. Assuming no typos or
> > other obvious syntax errors, will the Fill procedure work in Ada 83?
> >
> > package Zoo is
> >
> >   type Animal_ID is range 1 .. 5; -- yes, an enumeration type might be
> 
> I assume that the tricky part is that the attribute 'Succ operates
> on the base type of Animal_ID, which is of type integer, and does not
> consider the constraint 1 .. 5 (although the attributes 'First and

This didn't sound right to me, so its LRM time...

3.5.4 -
the type declaration is equivalent to -

   type integer_type is new predefined_integer_type;
   subtype Animal_ID is integer_type range 1..5;

where integer_type is an ananoymous base type, snd predefined_integer_type
can be any predefined integer type the compiler wants, as long as it 
includes 1 and 5.

Thus the base type is NOT integer. However, the base type's range may well
be the same as integer's.

3.5.5(8) -

 Animal_ID'SUCC(Next_Animal) 

returns a value in the range of the BASE type of Animal_ID, which is the
range of whatever predefined type the compiler picked above. However, 
when this value is assigned back into Next_Animal, it is subject to a
constraint check on the 1..5 range. The constraint check doesn't HAVE to
happen, but it could.

-- 
T.E.D.          
                |  Work - mailto:dennison@escmail.orl.mmc.com  |
                |  Home - mailto:dennison@iag.net              |
                |  URL  - http://www.iag.net/~dennison         |