Mailing List Archive: Re: Creating functions with local variables

[REBOL] Re: Creating functions with local variables

From: joel:neely:fedex at: 2-Jan-2003 9:56


Hi, Robert,

Happy New Year!

Interleaved below are a few hints that I hope are relevant (and not
too elementary/outdated to be useful to you... ;-)

Robert M. Muench
 wrote:
> > From: [rebol-bounce--rebol--com] [mailto:[rebol-bounce--rebol--com]]
> > On Behalf Of Anton
>
> >       context [myvar: id * 5 print myvar]
> >
> > context should automatically pick up set-words
> > and bind them to the new local context.
>
> Hi, I played around with context too but wasn't able to get it to work
> as I liked. Here is what I tried:
>
> dice2: 3
>
> test: context [
>         dice2: 2
>         action-with-var2: [dice2: 2 print ["Dice2:" dice2]]
> ]
>
> ?? dice2
> ; >> dice2: 3
>

Since DICE2 appears as a set-word inside the MAKE OBJECT! that word
is bound to the new context and (inside ACTION-WITH-VAR2) will be the
local one, rather than the global one ...

> But if you comment one line:
>
> dice2: 3
>
> test: context [
> ; ###   dice2: 2
>         action-with-var2: [dice2: 2 print ["Dice2:" dice2]]
> ]
>
> ?? dice2
> ; >> dice2: 3
>

... hence the difference obtained when the set-word is commented
out in the object definition.

> So you still have to mention all local words. And you have to agree
> on a function that gets called because the context will be an object
> that doesn't execute any code if used. You have to explicitly call a
> word from the context.
>
> The problem with your approach is: How do you execute it at runtime?
> It only works if pasted to command line.
>

Here is a little sample that uses multiple tricks to work around some
of the issues that I inferred are in play here:

8<--------
REBOL []

glofun: none

do in make object! [
    counter: 0
    set 'glofun locfun: func [] [counter: counter + 1]
    configure: func [n [integer!]] [counter: n]
] 'configure to-integer now/time
8<--------

I saved the above in a file named "glopri.r" and then called for it
to be evaluated, with the following results:

    >> do %glopri.r
    Script: "Untitled" (none)
    == 35292
    >> glofun
    == 35293
    >> glofun
    == 35294
    >> glofun
    == 35295

Hope this helps!

-jn-