Re: Ideas for Ada 200X

[Bill Findlay <yaldnifw@blueyonder.co.uk>]

On 31/5/03 12:42, in article uisrrnxzk.fsf@wanadoo.fr, "Pascal Obry"
<p.obry@wanadoo.fr> wrote:
> 
> Right! I must be a bit tired to forget that :) So I think it could be
> /:= *:= +:= and -:= (operators before the :=).

What about and, or, xor, rem and mod? "mod:=" ? I hope not!

I find this proliferation of special notations revolting.

An "idem" feature, meaning, "the same as the destination" and used thus:

1.  I := (idem + 1);  -- or perhaps: (<> + 1); or maybe: (all + 1);

2.  I := (1 - idem);  -- N.B. not possible using any ?:= operator

3.  X := 0.5*(idem + a/idem);

gives a lot more expressive power than update-in-place operations, but
allows the latter to be implemented very easily in most cases that
significant efficiency gains are possible (though not, admittedly,
arithmetic operations overloaded on matrices and other structures for which
conventional, if slightly heavier, procedural notations remain).

The idem notation also documents the programmer's intention more clearly in
the cases (such as 3) in which the RHS subexpression is necessarily the same
as the LHS, but which do not fit the limitations of a ?:= operation.

-- 
Bill-Findlay chez blue-yonder.co.uk ("-" => "")