Re: (elementary question) Test on type ?

[Ted Dennison<dennison@telepath.com>]

In article <9n2l16$bqv$1@nh.pace.co.uk>, Marin David Condic says...
>
>What you are trying to do is basically impossible in Ada. You can't have a
>generic parameter that is, say, "private" and then try to test to see if the
>actual is of type Integer or Float. There are a couple of reasons for this:

Actually it is doable, if the type in question is a tagged type. In that case
you can easily do something like:

if Object_A in Parent_Type_X'class then ....

The reason this won't work for Integer is that Integer isn't tagged. Thus:

1) You can't use 'Class on it (or a subtype of it).
2) You can't pass it into a routine that can also take other types for the same
parameter.

I suppose you would be able to do that with Integer if Ada had a type system
where every type was derived from some common root type. I think there are some
languages out there that work that way. Ada just isn't one of them.


---
T.E.D.    homepage   - http://www.telepath.com/dennison/Ted/TED.html
          home email - mailto:dennison@telepath.com