[REBOL] Re: Forward References
From: al:bri:xtra at: 14-Dec-2001 19:28
-richard- wrote:
> --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."
> How do you determine if the referenced function is "evaluated" before it
is defined? Must you order all definitions within a file so that the
definitions always come before reference is made to them? Any
references/weblinks with clarification?
Here's an example from the console:
>> f1: func [x] [print "F1" f2 x]
>> f2: func [x] [print ["F2" x]]
>> f1 4
F1
F2 4
Note that the function refered to by 'f1 refers to 'f2, and note that the
function refered to by f2 isn't created until the next line.
Here's new console session:
>> f1: func [x] [print "F1" f2 x]
>> f1 2
F1
** Script Error: f2 has no value
** Where: f1
** Near: f2 x
Note that in the second line I _haven't_ defined 'f2, but instead 'f1 is
evaluated. Note that Rebol says 'f2 has no value.
Everything that applies to a console session applies to a script.
I hope that helps!
Andrew Martin
ICQ: 26227169 http://valley.150m.com/
