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Subject: Re: in defense of GC
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From: Ray Blaak <rAYblaaK@STRIPCAPStelus.net>
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Date: Mon, 05 Feb 2007 01:00:08 GMT
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Date: 2007-02-05T01:00:08+00:00
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Robert A Duff <bobduff@shell01.TheWorld.com> writes:
> But in the latter, case, the return of Stepper is causing the lifetime
> of an integer VARIABLE (i.e. mutable) to be longer than one might
> suspect for a local variable of Make_A_Stepper.  That seems like a
> problem to me.

Yes, the lifetime is longer (as specified by the programmer) but the global
visibility is not affected -- N still cannot be directly manipulated in a
global sense.

> You (Markus) seem to be an advocate of (possibly-upward) closures.
> And also an advocate of function programming.  So how would you like a
> rule that says the former example is OK, but the latter is illegal?
> (That is, upward closures are allowed only when you're doing functional
> (no side-effects) programming).

I like general closures akin to the style of Lisp. It is interesting that
JavaScript, for all its faults, at least has fully general closures.

C# delegates are now essentially the same thing, and have full GC support.

Java's are busted due to implementation laziness.

So why not have general closures in Ada? They are a very powerful concept, and
one still gets the control if needed by simply not using them if appropriate.

But to do closures properly, one really does need GC.

-- 
Cheers,                                        The Rhythm is around me,
                                               The Rhythm has control.
Ray Blaak                                      The Rhythm is inside me,
rAYblaaK@STRIPCAPStelus.net                    The Rhythm has my soul.