[REBOL] Re: vargs function (or "r-expression)
From: tim-johnsons::web::com at: 7-May-2007 8:22
On Monday 07 May 2007 10:52, Gabriele Santilli wrote:
> > example:
> > do [vargs "two" 3]
> > do [vargs "two" 3 "four"]
> > do [vargs "two" 3 none "four"]
> > do[vargs]
>
> You can also just call it with:
>
> (vargs "two" 3)
> (vargs "two" 3 "four")
> (vargs)
>
> etc. (More Lispy. ;)
>
> However, I don't think this is a great idea when you have many
> arguments, and it'll cause problems if you forget the parens. If you
> need variable nuber of arguments, the best way is:
>
> vargs: func [args [block!] /local a b c] [
> set [a b c] reduce args
> ?? a ?? b ?? c
> ]
>
> >> vargs []
>
> a: none
> b: none
> c: none
> == none
>
> >> vargs [1 2]
>
> a: 1
> b: 2
> c: none
> == none
>
> >> vargs [2 + 2 3]
>
> a: 4
> b: 3
> c: none
> == none
>
> This is the starting point to make your ARGS block a dialect. :)
Thanks Gabriele. That is the elegant way to do it as stand-alone
code.
The function type I am referring to will be used as part of an automatically
generated code set. I thought about using the "unset" method to cut down
on "clutter" if visual expection was done.
Example:
[eval [prn "total_charge" 0 ]]
^ ^ function
| arbitrary marker. Just means "'do the following block"
[literal "just a string"]
^
| arbitrary marker. Just means use the following string as-is.
[eval [prn ["total_charge" 0] ]] ;; Gabriele's method.
I like your method better for the coding of the function itself.
cheers
tim
--
Tim Johnson <tim-johnsons-web.com>
Palmer, Alaska, USA
