Yes, Larry,
> > I feel, that Joel tried to warn us, that the "Poor man's module" is not
as
> > reliable as some may need it to be:
> >
> > Rebol []
> >
> > make object! [
> > protected1: 1
> > protected2: 2
> > if true [
> > unprotected1: 3
> > ]
> > ]
> >
> > and he is right, because 'protected1 and 'protected2 will not destroy
> their
> > global context couterparts, but 'unprotected1 can!
> >
>
> Your example illustrates that:
>
> 1) code in an object definition is executed
> 2) within an object definition we have access to all parent contexts up to
> and including the global context.
>
> It is consistent with my own (perhaps poorly worded) description:
> [
> There are stages in object creation, and in one of the early stages the
> object spec block is scanned for all first-level set-words. A context for
> the object is created with these words bound to it.
>
> After this stage, the code in the object spec is executed, in exactly the
> same way as a block of code in the global context. The only difference is
> that those words which occurred in the spec-block as set-words are bound
to
> the objects context. Any code can appear and will be executed.
> ]
your description is accurate. Just a little warning for the unaware:
spec-block: [a: 11]
spec-block-copy: copy spec-block
; now the contents of the Spec-block-copy is exactly the same as the
contents of the Spec-block:
all [
same? first spec-block first spec-block-copy
same? second spec-block second spec-block-copy
] ; == true
o: make object! spec-block
; now the contents of the Spec-block-copy is not the same as the contents of
the Spec-block:
all [
same? first spec-block first spec-block-copy
same? second spec-block second spec-block-copy
] ; == false
; this example illustrates, that the Make Object! function modifies its
Spec-block argument,
; although the change is invisible for the naked eye, because:
all [
equal? first spec-block first spec-block-copy
equal? second spec-block second spec-block-copy
] ; == true
The same property holds for the Use function too.
>
> UNPROTECTED1 is not a first-level set-word, so it is not in the objects
> context and thus no protection of global namespace is implied.
>
> The IF statement is just a piece of code which is executed when the object
> is created, it has access to the global context and can define or redefine
> any global (or object variable).
>
> It seems to me that we have pretty good control over our contexts. If we
> want UNPROTECTED1 to not affect the global context, we just add
> UNPROTECTED1: none in our object, making it a first-level word.
Correct, we do have a pretty good control over our contexts. What I wanted
to underline is, that we are not protected against our own omissions.
> REBOL currently is based on a context hierarchy, where nested funcs and
objs
> have access to words in all the higher levels of the hierarchy, as well as
> those in their own context.
The last statement is very questionable to me. I wrote
http://www.sweb.cz/LMecir/contexts.html
to prove, that there is only a Virtual Context Hierarchy in Rebol, i.e.
Rebol contexts aren't hierarchical at all.
Regards
Ladislav
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