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[REBOL] Re: Model hacking

From: joel:neely:fedex at: 22-Jun-2001 12:56

Ladislav Mecir wrote:
> Another one: > > 5) SYSTEM vs. USER -- Some types are predefined by REBOL and > the user cannot create values of that > type (e.g., op!) while other types can be created at will > by the user's expressions (object! and function!) > > 6) CLOSED vs. OPEN -- Some types (logic! and datatype!) have > a set-in-concrete set of possible > values, while others are open-ended and new values may be > created at will (function! and block!) > > 5) and 6) look like being "unifiable" >
I pondered that issue, and freely admit that I decided to separate them primarily on philosophical grounds. (However, I was in a hurry and confused the issue by a VERY poor choice of examples.) Let me go to extremes first: LOGIC! - Not only "closed", but closed "in principle". It wouldn't seem to make sense for RT to release a new version of /core or /view with new values of this type. BLOCK! - Open "in principle". Anyone may evaluate code that creates a block that has never existed before (with arbitrarily high probability, at least ;-)
>> reduce ["Joel's birthday might be"
[ to-date reduce [random 2000 random 12 random 31] [ "which would make him" [ random 2000 [ "years old" [ ] == ["Joel's birthday might be" 6-May-0283 "which would make him" 489 "years old"] In between those extremes are: EVENT! - I thought I saw an email about users not being able to create events. Whether memory serves me correctly or not, it seems that "in principle" RT could define a datatype that could be created by the interpreter but not directly by the user. OP! and NATIVE! - Although a given release has a finite, specific set of these, each new release can (and usually does) contains an expanded set, drawn from a seemingly inexhaustible fount which remains beyond the reach of mere mortals! (The DATATYPE! type should have been in this category, but I rushed through my typing too quickly. Mea culpa!) Now for the slightly more controversial cases ;-) CHAR! and INTEGER! - I propose that these are CLOSED (in that the set of *possible* character and integer values are finite) but USER (in the sense that I can make one whenever I want). One issue wrt calling INTEGER! a closed type is that if RT were to add a BIGNUM! type (integral of arbitrary precision) to a future version of REBOL, I'd think of BIGNUM! as OPEN/USER (no a priori upper limit, except for the size of your swap file ;-) -jn- ------------------------------------------------------------ Programming languages: compact, powerful, simple ... Pick any two! joel'dot'neely'at'fedex'dot'com