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[REBOL] Re: [datatypes] action! vs. native! vs function!

From: g:santilli:tiscalinet:it at: 23-Nov-2003 11:18

Hi Joel, On Saturday, November 22, 2003, 11:15:09 PM, you wrote: JN> Does anyone know the difference between NATIVE! and ACTION! JN> types? The list of the types in the ANY-FUNCTION! pseudo-type is: native! action! op! function! As you say, FUNCTION! values are the one we can create. ACTION!, OP! and NATIVE! values are "built in" in the interpreter, and we cannot create them. The distinction between the three is a little subtle, and is mainly an implementation issue I think (IIRC, Carl once said this, too). NATIVE!s are the "primitives", as you say. ACTION!s are those primitives that are actually "methods" (to use terminology from other languages) in other datatypes; that is, while for a NATIVE! there is one C implementation inside REBOL, for an ACTION! there can be more than one implementation; for example, PICK on a PORT! is different from PICK on a BLOCK!. While doing what you call "particle physics", I and others also discovered this:
>> second :print
== none
>> second :pick
== 40 While NATIVE!s do not have a "second" element, ACTION!s do, and it is a number; our guess (and I think it was more or less confirmed by RT) is that that number is actually an index in a function table for the datatype. Finally, OP!s are the infix version of ACTION!s (I'm not sure, as I haven't checked, if OP!s only map to ACTION!s or if they can map to NATIVE!s too). Being of type OP! is not enough to be treated as an infix operator by REBOL, as this is the only place where the function interpreter is "keywordized"; that is, only a number of pre-defined words can be OP!s. HTH, Gabriele. -- Gabriele Santilli <[g--santilli--tiscalinet--it]> -- REBOL Programmer Amiga Group Italia sez. L'Aquila --- SOON: