Re: Typing in Ada

["David C. Hoos, Sr." <david.c.hoos.sr@ada95.com>]

But both examples for C disregard the fact that int, enum,
and char can be freely mixed, something that Ada would
never allow.

"Peter C. Chapin" <pchapin@sover.net> wrote in message
news:Xns94FAA347BFEA8pchapinsovernet@207.106.93.237...
> Jeffrey Carter <spam@spam.com> wrote in news:mxJuc.18113$be.10152
> @newsread2.news.pas.earthlink.net:
>
> > procedure Strongly_Typed is
> >     type I1 is new Integer;
> >     type I2 is new Integer;
> >     type I3 is range -100 .. 100;
> [snip]
> >
> > int main () { /* I cannot call this Strongly_Typed */
> >     typedef int   I1;
> >     typedef int   I2;
> >     typedef short I3;
>
> This isn't an entirely fair comparison because in C, typedef doesn't
> introduce a new type it simply creates a new name for an existing type. In
> Ada, it would be more similar to using a subtype, perhaps. Something like
>
>      subtype I1 is Integer;
>
> In any event to create a new type in C you need to introduce a structure.
In
> fact, different structures do have different types:
>
> typedef struct {
>   int x;
> } A;
>
> typedef struct {
>   int x;
> } B;
>
> int main()
> {
>   A a;
>   B b;
>
>   a = b;  // Error. A and B are different types.
>
>   ...
>
> I'm not sure if there is a formal definition of strong typing or not. I've
> always thought that it had to do with the property of every expression and
> variable having a well defined type. If so, that is as true of C as it is
of
> Ada (in some ways its even more true of C because in C literal numbers
have
> specific types... there is no "universal integer" type used, for example,
for
> integer literals). The real difference is that C does a bunch of automatic
> type conversions and, furthermore, normally performs these conversions
> without checking if the converted value will fit into the target type. I'm
> not sure that's a strong typing issue, however.
>
> Peter
> _______________________________________________
> comp.lang.ada mailing list
> comp.lang.ada@ada-france.org
> http://www.ada-france.org/mailman/listinfo/comp.lang.ada
>