Re: A question and a request

["Matthew Heaney" <mheaney@on2.com>]

"Eric Merritt" <cyberlync@yahoo.com> wrote in message
news:mailman.1005116423.21054.comp.lang.ada@ada.eu.org...
> The addition operator is taking two disparate but
> related types and adding them.

You have to be careful about how you use the terms "type" and "subtype".
The (sub)types you defined simply name subsets of a common type.

> This is fine,
> up-casting is a normal thing. However, when the result
> is returned it is not (should not be?) an instance of
> the subtype.

The addition operator looks like this:

   function "+" (L, R : Integer'Base) return Integer'Base;

Only a "type" has operations.  Subtypes merely name a range of values within
the scalar type.

Your addition operator is returning a value in the set (whose values are
named by the type).  Then there is an assignment, which checks to make sure
the value (on the RHS) lies in the range of the subtype (of the object on
the LHS).

> It seems that the compiler is
> down-casting automatically. This bothers me and it
> seams that is violates Ada's strong typing. What am I
> missing here?

No, it does not, because there is only one type: the type whose first named
subtype is Integer.