[REBOL] Re: Forward References
From: ingo:2b1 at: 14-Dec-2001 10:37
Hi Richard,
Once upon a time Richard Boyd spoketh thus:
> The REBOL/Command User Guide page 8-29 states ..
>
> --Forward References--
> "Sometimes a script needs to refer to a function before it has been
> evaluated. This can be done as long as the variable for the function is
> not evaluated before it is defined."
<..>
> -------------- REFERENCE AFTER FAILS ------------------
> REBOL [Title: "Forward Reference"]
>
> view layout
> [banner "Forward Reference Test"
> button "New Pane" [open-new-pane]]
>
> open-new-pane: func
> []
> [view layout
> [banner "New Window"
> button "Quit" [quit]
> button "Unview" [unview]]]
> --------------------------------------------------------------------
In your example, once the 'view function is reached, the value
of open-new has to be present, because part of the script _after_
view, are only reached after closing the view window.
e.g.:
--------- Script 1 ------------
REBOL[]
print 'before
view layout [ label "hi" ]
print 'after
-------- Script 1 -------------
If you run this script, first 'before is printed, _then_ the window
is opened, and 'after is only printed, if you close the window.
The proper way to forward reference for you would be to create a new
word holding the layout until it is viewed, like this:
-------- Script 2 -------------
REBOL []
lay: layout [
banner "Forward Reference Test"
button "New Pane" [open-new-pane]
]
open-new-pane: func [][
view layout [
banner "New Window"
button "Quit" [quit]
button "Unview" [unview]
]
]
view lay
-------- Script 2 -------------
Now all functions are defined, before they are needed (evaluated) in
the 'view function.
I hope that clarifies it a bit.
Kind regards,
Ingo
