Re: What evil would happen?

["Robert I. Eachus" <rieachus@attbi.com>]

Randy Brukardt wrote:

> I've toyed with adding a mode to Janus/Ada to allow in out parameters on
> functions, but I haven't seen a compelling use for it (the most valuable
> uses would be in Claw, but that has to work with standard Ada).

And AFAIK, GNAT still supports the "value returning procedures pragmas 
from DEC Ada.

But the rule still won't change, and the reason is not just "politics." 
  This is just one area of the Ada programming culture that seems to rub 
foreigners (to Ada) the wrong way.  If you are used to Ada, the current 
Ada idioms for the few cases that seem to some people to be problems are 
natural to you.

Since I have done a lot of work on random number generators, the Ada 
idiom now seems natural to me:

function Random(Gen: in Generator) return ...
   Local: Generator;
   for Local'Address use Gen'Address;
begin
   ...
end Random;

Unlike RBKD, I did strongly argue for an in out parameter mode for 
functions in Ada 9X.  But in doing so I knew that it would be misused 
more than it would be correctly used.  By now with good implementations 
of Unbounded_String, most of the real needs for functions with in out 
parameters have gone away.  You can always declare a procedure with an 
out parameter of Unbounded_String.  So if the question is reraised I 
will vote against it.  And I will also vote in favor of a generic that 
provides the equivalent of Unbounded_String for all array types, 
including multidimensional array types.

-- 

                                                 Robert I. Eachus

�In an ally, considerations of house, clan, planet, race are 
insignificant beside two prime questions, which are: 1. Can he shoot? 2. 
Will he aim at your enemy?� -- from the Laiden novels by Sharon Lee and 
Steve Miller.