Re: GCC 4.0 Ada.Containers Cursor danger.

[Georg Bauhaus <bauhaus@futureapps.de>]

Mikhail Terekhov wrote:
> Matthew Heaney wrote:

>> You want to legislate behavior for everyone.  This is wrong.  You should
>> only be concerned with your own behavior.
> 
> 
> I unerstand this as "shut up and go away". This is not polite. Try to 
> apply the above three sentences to yourself.

I think you misunderstood. "You should only be concerned with
your own behavior" is also a technical argument.
You can use a language like SETL2, APL, or Haskell and then notice
that it is hard, if possible, to get anywhere near the
machine. For Ada.Containers, there is a machine model that
Matt has been mentioning many times. A machine model blends
rather well with Ada IMHO.

These VHL languages are not Ada (perhaps the response by Robert
Eachus illustrates?), and you don't necessarily expect pointers
or bit fiddling to be available in a very high level language
like SETL2 etc. Programmers writing programs in these languages
are not primarily concerned with the machine and that's why
these languages are not concerned with the behavior of programmers
even though they don't usually provide pointers and bits.

Using SETL2 you can write

 procedure quicksort(s);  -- a sorted list of the elements in set s
 begin
    if #s = 0 then
      return [];
    end if;
    pivot := arb s;
    return quicksort({e: e in s | e < pivot})
      + [pivot]
      + quicksort({e: e in s | e > pivot});
 end quicksort;

That's fine in the absense of time and when s is not a large set.[*]
But absence of timing and memory usage requirements is unlikely a typical
Ada situation? So in Ada, I'm comfortable with element related algorithms
working at a less higher level of abstraction, as I'm trying to control
a machine.

 [*] So I guess is't fine for non-temporal mathematics.

-- Georg