Re: Update-in-place assignment

[Hyman Rosen <hyrosen@mail.com>]

Bill Findlay wrote:
> The trouble with the C* "?=" operators, and the derivative proposals made in
> this thread, is that they provide a very restricted subset of a much more
> general facility.
> 
> E.g. we might have  i := idem -1;  or i := 1 - idem;
> or even  x := 0.5 * (1.0 + a*idem);
> 
> What that does not give the C* people is maximal brevity.
> The extra expressiveness should more than compensate.

No. What it *also* does not give the C++ people is a place
to write the code to handle the operation efficiently!
The designer of a class can provide the ?= operators for
that class, and write the code to perform the operation.

With your suggestion, we have the expressiveness, but we
can't do anything with it. If the only goal is to avoid
mentioning a long name more than once, C++ has its version
of a renaming clause just like Ada does:

	double &d = myStruct.itsArray[7].itsPoints[15].z;
	d = (1 + d) / (1 - d);