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[REBOL] Re: On mutability and sameness

From: joel:neely:fedex at: 21-Jun-2001 4:00

Hi, Mark, [Robbo1Mark--aol--com] wrote:
> The point is that Ladislave, yourself & others debated >
How about "discussed with great energy"? ;-)
> at length, trying to use only REBOL and a natural language > ( English ) to demonstrate the differences in property & > behaviour of SAME? & EQUAL? functions. >
Did my little story about "same" and "equal" bank accounts capture that distinction for you? If not, I'd really like to think about how to improve it. If so, then it shows that we can discuss conceptual distinctions without resorting to low-level programming languages.
> Using REBOL was insufficient in producing a function for > testing whether an any-string! or any-block! value shared > the same memory location, >
I'm really distressed with myself for being unable to state this point clearly enough. WRT series value: I do not CARE whether two series values share "the same memory location" (and I especially do not care how many bits are in that "location" nor how it may be laid out). What I care about most is this: Given two expressions (including simple words) that each evaluate to a series, under what conditions can I perform an evaluation involving one of them that has the effect of changing the evaluation of the other? I also care (somewhat less) about this: Given two expressions (as above...) can one of them consistently be evaluated using less time and/or memory than the other? It is not hard to demonstrate that two expressions may evaluate to the "same" series, and to start drawing inferences as to when that occurs.
>> a: [1 2 3] == [1 2 3] >> b: a == [1 2 3] >> c: [1 2 3] == [1 2 3] >> d: copy a == [1 2 3] >> reverse a == [] >> a == [3 2 1] >> b == [3 2 1] >> c == [1 2 3] >> d == [1 2 3]
Some conclusion about copying and literal series expressions are fairly obvious, and I won't take the time for them here. Factors that make this game more subtle include: 1) the rich variety of REBOL data types, 2) REBOL's ability to create self-referential structures, and 3) the desire to discover "non-destructive" tests that preserve the values we're examining. (Old joke: How can you tell if a chair is an antique? It burns with a bright blue flame!)
> and natural language was to ambiguous and lead to discussions > about concise definitions & meanings for words. >
... to which the solution involves precise definitions, mathematics, and logic, not another programming language. I must also point out another of my hidden biases. I regard the goal of "a programming language for non-programmers" in the same light that I regard the strong-AI goal of programming human-like intelligence. I believe that both are ultimately impossible. HOWEVER, I believe that efforts toward both goals have led to wonderful advances in the state of programming that likely never would have happened otherwise. If you'll pardon the sports analogy (I'll probably regret this as well ;-) it's perfectly OK for a runner to set the goal of running a 2-minute mile, and to develop nutrition and training regimens shaped by that goal. On the other hand, if a runner claims to me that (s)he actually *has* run a 2-minute mile, I'm going to get very, very picky about examining his/her stopwatch and yardstick, and I'm going to insist on an actual, testable demonstration before I accept the claim. (And even then I'll be suspicious... ;-) The AI community lost their credibility (despite some really wonderful achievements) due to overselling and overly- optimistic/enthusiastic claims. AI fell from being a leading frontier in computing to being a marginalized niche, and its proponents are now often viewed as snake-oil salesmen. I don't want to witness that kind of tragedy again. Especially not with REBOL. I have great respect for Carl and the whole RT team, and for the fruits of their labors. That's why I often (usually?) take on a gadfly-like role and challenge the notions that (what I regard as) hand-waving explanations (or *no* explanations, in some cases ;-) and claims of simplicity are good enough to certify REBOL as a final achievement of the "impossible dream" of easy programming for non-programmers. Better stories, more precise language, more complete documents (written *both* by RT and the user community) and, yes, the elimination of some unnecessary inconsistencies in REBOL itself will all move us toward better programming for both programmers and "non-programmers". Requiring that we describe REBOL in terms of a low-level programming language is IMHO contrary to that goal.
> Your use of C, whilst admittedly not making it clear to > everyone, showed demonstrably the why & how of the different > behaviour. Anyone who knows C could study your example and > see the logic that produced the REBOL like behaviour... >
This is the heart of the problem (and the reason for my sincere regret over that example!). One or two of the questions in the thread seemed (to me) to imply that REBOL was drawing a peculiar distinction that was outside normal programming concepts. Quod non. I wanted to show that the distinction does exist in other languages, but that REBOL expressed it differently. I wasn't trying to argue "how" REBOL must have been implemented. For the rest, please reconsider my posted remarks on the danger of drawing triangles in geometry. Arguing by example runs the severe risk of having irrelevant details of the examples take over the discussion and focus attention on the wrong details. Depending on The Language That Must Not Be Named as our means of explaining REBOL: 1) brings in entirely too much irrelevant baggage, 2) can be misleading, and 3) excludes anybody who doesn't already know that Language. I consider all of these to be undesirable.
> All I will say is how advanced would our understanding of > modern science be if the discoveries of Newton, Einstein, > Planck, Maxwell etc. were proprietary & secret? >
How advanced would our scientific understanding be if: 1) NEPMetc. were *required* to do all of their thinking in public, subject to constant committee-style debate over every detail while the work was still in progress? 2) Einstein, Bohr, and Planck were *required* to explain all of their ideas strictly in terms of Newtonian mechanics, and told that anything that didn't fit the Newtonian model was unreasonable and unacceptable? Now (to follow my own advice) I'm back to model hacking! -jn- ------------------------------------------------------------ Programming languages: compact, powerful, simple ... Pick any two! joel'dot'neely'at'fedex'dot'com