Mailing List Archive: 49091 messages
  • Home
  • Script library
  • AltME Archive
  • Mailing list
  • Articles Index
  • Site search

[REBOL] Re: On mutability and sameness

From: robbo1mark:aol at: 19-Jun-2001 7:27

Joel Neely
< snip >
Iam not trying to reverse engineer REBOL......
< snip >
Ladislav Mecir
< snip >
Iam not trying to make discoveries or statements about REBOL implementation details.......
< snip >
; disclaimer, I'm not sure if I've quoted ; Joel & Ladislav here precisiely word for ; word, I don't have thier original postings ; & docs to hand, but I think these statements ; portray accurately what they were trying to ; convey. Sincere apologies if I misrepresent ; them in any way! With the utmost respect to both Joel & Ladislav whom I admire & respect both greatly, and thank them for the knowledge and insight I gained from them with their thoughtful & considered posts and documents. Having followed this thread with interest, I believe, barring the disclaimer above, that both Joel & Ladislav are WRONG in the sense that some REBOL behaviour can only be explained and understood fully in terms of the way it has been implemented. Now I know that both Joel & Ladislav and myself are all striving for basically the same thing. We want to REALLY UNDERSTAND REBOL. REALLY UNDERSTANDING REBOL means having an accurate model & conception of the structure of REBOL that can properly predict REBOL behaviour for any given function or datatype. To me this "understanding" means how REBOL is implemented as well. Now as we all know REBOL is not open source and only Carl & the RT gang can truly know it's inner secrets & full implementation details & specification. Holger Kruse also stated that users shouldn't speculate about the precise implementation details as this can vary between CPU, platform etc. This is a valid point in as much as it is true however it does not aid us in our quest to understand REBOL and it puts us in a position of dependancy on RT to clarify further or reveal parts of REBOL secrets / mystery we don't fully grasp. Sometimes they are very good and they do explain things more fully at other they say either nothing or nothing helpful as it may impinge on REBOL's proprietary-ness. Joel & Ladislav both find areas where the existing REBOL documentation and / or REBOL behaviour is either misleading, inconsistent, confusing, not fully or properly documented, or sometimes in their opinion wrong! Though they sometimes disagree / agree to disagree, and appear to come at things from conflicting angles or viewpoints, in essence they strive for the same thing and that is to UNDERSTAND REBOL and be able to describe / document concisely and comprehensively ( and consistently ) REBOL values and behaviour. Forgive me if Iam wrong, but I think Joel is seeking a fully comprehensive understanding and Ladislav seeks clarity, simplicity, purity and consistency. These are NOT mutually exclusive. However I think they are wrong to believe they can fully and properly achieve this without geting down to the nitty gritty of implementation details where necessary. To fully understand the behviour of any-block! or any-string! series! values you have to have a model of how series! values are implemented at the C code level from which REBOL is built. The behaviour of series! and their associated functions are direct result of the way they are implemented in C. The same applies to whether set-words or set-paths etc. create a new instance or copy of a value or merely reference existing value data. Whilst any C code model we might build for REBOL values, whether they be "simple" values like integer! or char!, series! values like block! string! etc. or compound values like date! time! tuple! etc. will most probably NOT exactly match the RT official implementation, I think it is important conceptually that we do TRY to conceptually build an implementation model. What is important is NOT that we precisely match the official REBOL implementation from scratch, that would be impossible as we are essentially working blind and cannot know all the platform specifics in advance. Rather it is important that we build our model then incrementally refine / modify & improve it in view of further tests, errors, new and better models. What in essence we are doing is subjecting our Model to a "Turing Test", if it is capable of producing the same results and behaviour as REBOL then for all intents and purposes it is a valid working model of REBOL, regardless of number of bits per value etc. Charles Moore of Forth fame has been quoted "To fully understand your tools you have to build / re-build them yourself from scratch." Now Chuck Moore is famously an extreme perfectionist and harsh taskmaster but there is a strong element of truth and wisdom here. On the otherhand there is also the saying "if you want to create an omelette from scratch, you have to devise a way of re-creating the Big Bang". Hopefully we don't have to go that far back or that "low level" 8-) I liked Joel's recent example of an equivalence test using C code to display strings as char pointers, char arrays, variable references etc. This example showed how to produce a boolean true or false that mimics actual REBOL behaviour. Unless REBOL Technologies produce the "REALLY UNDERSTANDING REBOL" book subtitle: REBOL Implementation Explained for Tech. Experts & Hackers then to gain the knowledge and clarity we seek I think it's inevitable sometimes we will have look under the hood and build our model upwards from C code to properly understand and explain topics of debate and / or dispute, regardless of whether we get the bit numbers slighlty wrong. Just like my eyes and hair are brown is controlled by my genetics, REBOL is an extension of it's implementation in C. One is a direct result of the other. Credit to Joel, Ladislav and others for the high quality and insight of posts thus far. Cheers, Mark Dickson In a message dated Sun, 17 Jun 2001 1:44:03 PM Eastern Daylight Time, "Ken Anthony" <[kenneth--nwinet--com]> writes: << Joel, Much appreciation for your discussions in this list.
> Kind of datatype Comparison to be performed > ---------------- -------------------------- > 1) Simple data Compare the data values > 2) Reference data Compare the "pointer" values > 3) Reference data Compare the "final data" values > > > there a referenced? vs. non-referenced? type function? > > Not AFAIK. The following is a quick cut at a function that > tells whether the current value of a word is of a reference > type.
May I propose or suggest that RT consider adding a 'simple?' function (the word seems to be common to the thread whereas sharable? seems to add a nuiance not explicit in your chart above) which could act as a lawman for these issues.
> sharable?: func ['w [word!]] [ > found? any [ > series? get w > any-function? get w > object? get w > ] > ] > > It may be used as follows: > > >> a: "123" == "123" > >> sharable? a == true > >> a: 123 == 123 > >> sharable? a == false > >> a: 12:30 == 12:30 > >> sharable? a == false > >> a: [1 2 3] == [1 2 3] > >> sharable? a == true > > No warranties expressed or implied! I believe it to be true > for the "ordinary data" cases, but it may require tweaking > for the more esoteric REBOL-specific types.
But I *want* warranties! Deputy, round up a posse! I have a warrant here for any genius language designer that leaves too many undefined issues hanging around the saloon. I don't give a lick for what that there Godel hombre has to say about it. While we're at it, let's throw in a few divide by zero's laws just for kicks. It may be infinity to those there mathmatical fella's, but us programmer's around these here parts usually just define the result to be zero. But Sheriff, my boy told me that 0/0 is undefined soes we might as well make a law that it's ta be nought... wouldn't it be more correct for sum number there divided by nought to be a really big number like those mathmedical fella's says? Now deputy, if they want to test for zero, they can test for zero, but I'm telling ya we got ta have a civilized town here. That means no shootin' irons in the town limits and zero begets zero whether ya multiply or divide. Well I don't rightly know Sheriff, sounds kinda dangerous like to cipher thata way. BTW, Sheriff didya notice they got this cp thing that does the same thang as copy? I saw that there deputy, and I plan to make eunix atta those there rustlers as soon as we get this zero issue all cleared up. Now let's go down to the corral and see what Ike and his boys are up to. OK. Well of course.