Re: Question about generics.

["Jeffrey R. Carter" <spam.not.jrcarter@acm.not.spam.org>]

Peter C. Chapin wrote:
> 
> Why not a compile time error when the instantiation is attempted?

Because the legality of a generic unit is determined when the generic is 
compiled, not when it is instantiated. That the generic formal of Size 
allows non-positive values is yet another reason this specific example 
would be illegal, even if Size were static.

> Yes. However, this means at the point of instantiation I have to do 
> something like
> 
>     	type Dummy_Type is mod 8;
>     	package Fizzle is new Xyzzy(Index => Dummy_Type);
> 
> The Dummy_Type will never be used in the context of the instantiation; 
> it only exists to pass size information into the generic package. That 
> seems pretty counter-intuitive and awkward. I guess I was hoping Ada 
> would have a nicer solution... generic parameters that are named numbers 
> or something.

I find this hard to accept. The reason to declare a visible type in the 
generic is so that the client can use the type from an instantiation to 
call operations of the type provided by the generic.

-- 
Jeff Carter
"Now go away or I shall taunt you a second time."
Monty Python & the Holy Grail
07