[REBOL] Re: On mutability and sameness
From: joel:neely:fedex at: 17-Jun-2001 8:34
Ladislav Mecir wrote:
> I try to reformulate my argument: "your rule is correct only
> in the circumstances not specified by the rule"
>
> This is a sufficient condition for the rule to be considered
> incorrect.
>
I'm sorry. I guess I need more coffee this morning, but I
couldn't follow that one at all. Maybe we should bring this
one to a close on the note that we simply agree to disagree.
Each of us has a model for what is going on with respect to
references and mutability, and in fact we seem to have
differing definitions for those words. I've chosen the one
that I use because
- I think it give me a simpler way to explain a wider
range of REBOL phenomena,
- I think it is consistent with conventional jargon
in Computing Science, and
- it allows me to compare/contrast REBOL behavior with
that of other programming languages easily.
YMMV, of course, and you're certainly entitled to use and
promote a different model. I welcome any and all challenges
to the model I'm using (because that's how we find bugs!).
I think it's fair to call the model "incorrect" only if there
is a piece of REBOL code that produces a result/effect that
is different than the model predicts, using the terminology
of the model in the way that I've been using it.
As far as the case below:
a: [8]
bm [a/1/1: 1]
a ;== 9
all I can say is that BM is a very clever mini-interpreter
that re-interprets its argument block as if it had been
written
a/1: a/1 or 1
which -- in my model -- changes the first element of the
block (referenced by A) by replacing the integer 8 with a
different integer (9), and not by modifying the 8 in-place.
As ingenious as BM is (and I mean that sincerely!) it extends
set-path expressions in a way that is outside standard REBOL
behavior:
>> a: [8]
== [8]
>> a/1/1: 1
** Script Error: Cannot use path on integer! value
** Near: a/1/1: 1
and therefore doesn't prove anything about whether my model of
standard REBOL behavior correctly predicts standard REBOL
behavior.
Again, let me express my sincere appreciation for your deep
understanding of REBOL and for your discussions and time.
-jn-
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joel'dot'neely'at'fedex'dot'com
