Re: Ideas for Ada 200X

[Stephen Leake <Stephe.Leake@nasa.gov>]

"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> writes:

> I am not so sure that a compiler would be capable to optimize each
> possible case of X := X @ Y. Especially if all operations in the
> expression are user-defined and types are controlled.
> 
> On the other hand, very often in C++ to implement all that ++, +=,
> *= etc + by value vs. by reference variations becomes a heavy burden
> when an abstract type is defined. It is also difficult to ensure
> that the semantics of all operations is compatible.

Exactly. If you can't expect a compiler to get it right, why would you
expect a programmer to get it right?

Clearly for scalar types (reals, integers, enumerations),
Foo_type'Inc(by : in Foo_type) is simple to define and implement; not
that different from 'Succ. That would be a trivial addition to the
language, and I'd like to see it (if only to end this thread :).

But for user-defined component types (records, protected, array
types), the semantics can get too complex. What would Array_Type'Inc
(By : in Array_Type) mean? "Add By to each element" comes to mind, but
that's probably not very useful. 

Users can always write their own Inc function, anyway, so there is no
need to allow user-defined 'Inc.

-- 
-- Stephe