Re: Ada Successor Language

[Shark8 <onewingedshark@gmail.com>]

On Monday, June 18, 2018 at 3:27:13 PM UTC-6, ric....@gmail.com wrote:
> On Monday, June 18, 2018 at 5:20:32 PM UTC-4, Shark8 wrote:
> 
> > I'd honestly like the ability to use X'Type; this would allow us to say something like this:
> > 
> > [snip]
> > 
> > Yeah, I know, it's a little thing and you can do it with generics, etc. But that's not entirely the point, the point is that this allows the declaration of types dependent on objects... it provides some of the niceties of type-inference without having to resort to such lazy/possibly-error-prone methodologies.
> 
> 
> Why would you want that? You have to have visibility to the type to declare an object of the type. In your above example, you explicitly know about Some_Type, and you also explicitly know that A and B are of that type. So you don't need to query the parameter, since it is implicit.
> 
> Your example above has no purpose.

Unless you're rapid-prototyping.

> > Procedure Swap( A, B : in out Some_Other_Type ) is
> >   Temp : Constant B'Type := B;
> > Begin
> >   B:= A;
> >   A:= Temp;
> > End Swap;

One change in the above, no change-cascades into the body.

This is precisely why text is such a bad format to think of as "natural" for the 'source' -- it's not -- what we really have here problem-wise stated in plain language is: "Given some type, and two names referring to them, switch which names belong to which object."

But that brings up something else that would be nice, the ability to do a swap like so:

(a, b) := (b, a);

> Any other case where you wouldn't know about the type until runtime is exactly what generics are for.

Generics in Ada are statically known at compile-time, just as the given example.