Re: True faiths ( was Re: The true faith )

[Richard Riehle <richard@adaworks.com>]

Hyman Rosen wrote:

> Richard Riehle wrote:
>
> >         procedure Copy_Deep       (Source : in T; Target : in out T);
> >         procedure Copy_Shallow  (Source : in T; Target : in out T);
>
> I dislike the notion of providing these methods as external interfaces
> to a type. It seems wrong to me for a client to have to know what kind
> of copy to use - that's the type's business to know.

Well I don't like having an assignment statement that behaves in an
unpredictable way when I use it.   So I prefer having the copy semantics
spelled out as clearly as possible.    This clarity assures me that, when
I call a method, it will behave as I expected.    From my perspective,
clarity is an essential feature of a type.   Behaving according to my
expectations is another nice feature for any method, whether it is
assignment or some other method.

As to the client needing to know which copy to use,  in practice we
would make only one available, but we would make clear the semantics
of that copy.   The other point is that using Ada's limited types, we
don't have to worry about making mistakes regarding the assignment
operation.

Richard Riehle