[REBOL] Re: Obscure? You be the judge!
From: joel:neely:fedex at: 14-May-2002 7:57
Hi, Volker,
Thanks for the explanations. As Larry Wall said:
Just because something is obviously happening doesn't mean
that something obvious is happening.
;-)
However, I'm still left with a puzzled look on my face over
one aspect of this...
Volker Nitsch wrote:
> Hi Joel,
>
> >> a: context [ b: [1]]
> >> c: make a[]
> >> d: make a[]
> >> same? a/b c/b
> == false
> >> same? c/b d/b
> == false
>
> when you 'make an 'object!, all strings, blocks and functions are
> copied.
> that allows for example in 'layout :
> box with[append init[my-inits]]
> without destroying the original in box.
> also blocks, like functions, are rebound.
> so [make child-proto []] gives a copy of 'dataref, not the original.
> but objects are not copied,
> so the 'face/feel are all the same after [make face[]].
> or in your case,
(Oh, by the way, did you find this documented anywhere, did you
just figure it out for yourself, or is there another path to
enlightenment? ;-)
Thanks to your explanation, I have a more compact example...
gub?: make object! [
data: [1]
proto: make object! [
number: 0
dataref: data
speak: func [] [print [number mold dataref]]
]
things: []
append things make proto [number: 1]
append things make proto [number: 2 dataref: data]
tweak-n-speak: func [blk [block!]] [
insert data blk
foreach thing things [thing/speak]
]
]
...which behaves as follows...
>> gub?/tweak-n-speak ["OK,"]
1 [1]
2 ["OK," 1]
My remaining puzzlement is over this contrast:
If I accept the description that (during the construction of
GUB?/PROTO) GUB?/DATA is copied and GUB?/PROTO/DATAREF is set
to refer to the copy, then that explains the behavior of
GUB?/THING/1 .
However, during the construction GUB?/THING/2 the additional
spec block *also* refers to GUB?/DATA , but apparently the copy
behavior does *not* occur (even though the referenced data value
is still only a block).
This makes me wonder if the issue here is a difference in the
evaluation of the specblock parts of
make object! [...specblock...]
vs.
make some-object [...specblock...]
This is uncomfortably reminiscent of FORTH, in which one must
have a complete operational model of the interpreter's internal
state if one is to understand the behavior the more advanced
(and hence more useful) aspects of the language. At least FORTH
had both liberal documentation and available source to help with
the construction/communication of such an operational mental
model...
-jn-
--
; Joel Neely joeldotneelyatfedexdotcom
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