Re: Array type conversion

[Robert A Duff <bobduff@shell01.TheWorld.com>]

"Jean-Pierre Rosen" <rosen@adalog.fr> writes:

> A derived type needs not have the same representation as its ancestor type.
> If the subtypes statically match, the compiler can perform a simple memory
> copy.

Hmm.  I don't think that's right.  Even if the two array types have
identical component subtypes, one could have pragma Pack, and the other
not, which would require component-by-component copying.  Similarly, one
could have a different 'Component_Size specified.

>... Otherwise, the compiler must in effect generate the exact equivalent
> of the loop you give, and there is a deliberate decision in Ada to avoid, as
> far as possible, *hidden* inefficiencies.

That principle is often stated in the Ada world.  IMHO, it is not a good
principle of language design, and in fact Ada disobeys it more often
than it obeys.  And the cases where it disobeys are cleaner.

- Bob