[REBOL] problems with local vars??? Re:(2)
From: joel:neely:fedex at: 17-Aug-2000 4:20
Hi, Brett!
Being the nit-picky kind of guy that I am ;-) I'd like to suggest a
slight
change in the wording of your explanation.
[bhandley--zip--com--au] wrote:
...[snip]
> Here's your function slightly edited
>
> local-func: function [input][my-local-string][
> my-local-string: ; This says make it so that my-local-string refers
> to the next value. (1)
> "that is local " ; This says create a string value. (2)
> print append my-local-string input ; (3)
> ]
>
I think it's slightly confusing to say in (2) that the literal string
says to create a string value
. Instead, I suggest that in (2) the
literal string IS a string value. (If I had my geek hat on, I'd say
something more complicated like "serves as a reference to the string
that was created when this source code was loaded", bit I left my geek
hat at home today... ;-)
In many other languages, using a literal string causes a fresh string
value to be created whenever the containing code is executed. In the
REBOL code above, a string! value only gets created once -- when the
above code is loaded.
Every time the function referred to by to local-func is evaluated,
my-local-string is set to refer to THE SAME STRING, rather than a
newly-created one. Therefore, mutations on the value of my-local-string
(e.g., append, insert, remove, replace ) are continuing to operate
on the same string which ORIGINALLY (at load time) contained
that is local
, but which has subsequently been modified with every
evaluation of the function.
I don't want to sound hypercritical here! I'm really just thinking
out loud about how to describe the behavior of literal series values
in REBOL, as this sort of thing keeps coming up on the list. You
certainly described the correct solution in the remainder of your
note, but I'm wondering if making a more explicit distinction between
load time and evaluation time will help us explain this.
Anyone think so?
-jn-
