[REBOL] Re: Obscure? You be the judge!
From: joel:neely:fedex at: 18-May-2002 10:34
Hi, Ladislav,
Ladislav Mecir wrote:
> <<Romano>>
>
> 3) I did not test your code, but it seems to me that it bind the
> body function to the new context. This is only half correct:
> binding is done in Rebol before adding the new set-words of spec
> to the new object:
>
> d: "global"
> a: context [b: does [print d]]
> a/b; == global
> a2: make a [d: "local to a2"]
> a2/b; == global
>
> As you can see, the d word in the func body is not binded to the
> a2 context.
> But:
>
> a: context [b: does [print d] d: "local to a"]
> a/b; == local to a
> a2: make a [d: "local to a2"]
> a2/b; == local to a2
>
> <</Romano>>
>
> <<L>>
>
> Thanks for your analysis. This behaviour is really complicated.
> (I wonder what will Joel say to this?)
>
He didn't say anything. He just ran from the room screaming
incoherently!!! ;-)
Seriously, I wasn't nearly as surprised by this example as I have
been by some other "interesting" examples. Since encountering
REBOL I have been on a (non-terminating ;-) quest to find the
simplest possible model/principles from which to understand and
describe the behavior of the language. For example, once one
understands the way REBOL uses the concepts of "word" and "context"
it is follows very logically that in the following:
a: make object! [
p: 42
q: "Howzabout them apples?"
r: func [] [
pick q (length? q) // p + 1
]
]
b: make a [
p: 7
q: "I have nothing to say and I am saying it."
]
each of A and B must have its own copy of R with no code-sharing.
Similarly, the non-intuitive behavior of Romano's example above
can be explained fairly simply in terms of the "definition-time
binding" rule and the way MAKE OBJECT! treats top-level set-words
in the spec block.
>From my mathematical background, I don't see a contradiction in
simultaneously seeing something as "non-intuitive" and "simple"
because that background has taught me that intuition is trained
by experience. Something outside our everyday experience is
likely to be non-intuitive/surprising more from our unfamiliarity
with it than from its inherent complexity. Given the fact that
different people have different styles of thinking and learning,
I conclude that the best way to teach something unfamiliar is to
use a combination of *both*:
* axiom-like basic principles from which the behavior of the new
thing can be deduced (for obsessively top-down, deductive
thinkers like me), and
* cumulative experience, beginning with simple examples and
leading up to the more out-of-the-ordinary cases (for the folks
at the other end of the thinking-style spectrum who are more
bottom-up and inductive).
I'd love to write such an introduction to REBOL one of these days,
but feel compelled to learn it better myself before doing so. I
also would like to feel a high level of confidence in the stability
of the core language concepts. The upcoming dosage of Valium to be
adminstered to word evaluation would certainly have made some of my
previous models and descriptions inaccurate! ;-)
-jn-
--
; Joel Neely joeldotneelyatfedexdotcom
REBOL [] do [ do func [s] [ foreach [a b] s [prin b] ] sort/skip
do function [s] [t] [ t: "" foreach [a b] s [repend t [b a]] t ] {
| e s m!zauafBpcvekexEohthjJakwLrngohOqrlryRnsctdtiub} 2 ]
