Re: proposal for new assignment operators

[Richard Riehle <richard@adaworks.com>]

Kevin Cline wrote:

> I found the distinction between controlled and uncontrolled types to
> be completely obscure and to my mind completely unnecessary,
> particularly when compared with C++, where one simply overrides the
> assignment operator if desired.

One reason for the peculiarity is that Ada, unlike C++, has limited
types.   For limited types, assignment is never possible.  Therefore,
overloading assignment is not possible.   Limited types are used for
most container classes.

It is rare that one even needs to override the assignment operator
on a non-limited type.   There is a distinction here that will not
be immediately obvious to the C++ programmer.

Additionally, the idea of Adjust for overriding assignment was done
intentionally after much wrangling about whether the language should
allow direct overriding or overloading the assignment operation.  For
a lot of very good reasons, the designers eschewed the C++ approach
in favor of the Adjust approach.   These reasons are discussed in some of the
literature that covers the rationale for the language design.

Richard Riehle