[REBOL] Re: Pointers, Context in Rebol 3.0 (For the real Rebol Lovers)
From: gabriele::colellachiara::com at: 24-Mar-2007 11:30
Hi Giuseppe,
On Friday, March 23, 2007, 9:17:11 PM, you wrote:
GC> aaa is no longer usable and it is reported to have no value. It seems rebol
GC> is not able to bind the new F1 to the context of the parent object.
It's not able to do so *automatically*. (And it shouldn't.) You
just need to use BIND.
>> o: make object! [f: does [a] a: 1]
>> o/f
== 1
>> f2: does [a]
>> o2: make o [f: :f2]
>> o2/f
** Script Error: a has no value
** Where: f
** Near: a
>> bind second :f2 o2
== [a]
>> o2/f
== 1
GC> There could be a way to change this situation in Rebol 3.0 ?
Short answer: no.
GC> a1: func [a b] [a / b]
GC> inst1: make template [f1: :a1]
GC> inst2: make template [f1: :a1]
GC> I expect that both inst1 and inst2 share the same "pointer to a1"
No - your model is just wrong here. You have three different words
and all refer to the same value. If you change the value a word is
referring, there's no reason why the value any other word is
referring should change.
a1 -----\
f1 --------> func [a b] [a / b]
f1 -----/
You are just changing the arrow for a1; this operation should not
have any effect on the arrows of the two f1. (They don't even know
about a1.)
(Please note that the above diagram is simplified.)
GC> Performing a:
GC> a1: func [a b] [a / b + 1]
GC> should change both INST1/f1 and INST2/f1 because they should point to the
GC> same function as I have declared [F1: :A1].
Just use something like f1: func [a b] [a1 a b] instead.
GC> For rebol 3.0 I ask you the ability to point to an external function like
GC> having a pointer to a function in C. Changing the pointed function should
GC> change the working of F1 in both the declared objects.
Changing the pointed function means something like:
change second :a1
and *not*
a1: some-new-thing
The latter does *not* change the "pointed" function.
GC> If you introduce the "pointer to function" concept in some way we could
GC> declare (for example) 10.000 object and change the working of their inner
GC> functions with a simple line of code because we have declared them as
GC> pointers and not locally copied.
They are *not* copied, they are the same function value. (And this
is actually a problem, because it can't be bound to different
contexts!) But changing the word does not change the value.
Regards,
Gabriele.
--
Gabriele Santilli <gabriele-rebol.com> --- http://www.rebol.com/
Colella Chiara software division --- http://www.colellachiara.com/
