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vargs function (or "r-expression)

 [1/6] from: tim-johnsons::web::com at: 6-May-2007 17:14

Hello Rebolers: NOTE: 'vargs is a "C" term where variable arguments are used and "r-expression" is a take on the lisp term: "s-expression". In lisp, you can have variable argument lists and the function call will be coded something like: (func arg1 arg2 arg3) I have a need for an "r-expression", that is - a class of functions that will be evaluated by 'do as part of a block and can have 0 or more arguments. example: do [vargs "two" 3] do [vargs "two" 3 "four"] do [vargs "two" 3 none "four"] do[vargs] I'm starting with this: vargs: func[arg1[string! unset!] arg2[integer! unset!] arg3[string! logic! none! unset!] arg4[string! logic! none! unset!]][ case/all[ value? 'arg1[?? arg1] value? 'arg2[?? arg2] value? 'arg3[?? arg3] value? 'arg4[?? arg4] ] ] This approach can work for me, I think, but I would welcome any comments, observations or caveats. thanks tim -- Tim Johnson <> Palmer, Alaska, USA

 [2/6] from: btiffin:rogers at: 7-May-2007 0:40

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 [3/6] from: btiffin::rogers::com at: 7-May-2007 0:45

I hope I'm not clogging, but the last reply I sent got sent back here as trash. It should read. Nice one Tim. I'm not sure of the better way of getting unset! in an expression but you can use do [vargs set/any 'a [do prin []] 2 false "four"] to skip setting arg1, (or arg2...) but you definitely don't skip any typing. Cheers, Brian On Sunday 06 May 2007 13:14, Tim Johnson wrote:

 [4/6] from: anton::wilddsl::net::au at: 7-May-2007 16:16

Use an empty paren: f: func [a [any-type!] b [any-type!]][print [value? 'a value? 'b]]
>> f 1
true false
>> f () 1
false true I sometimes put it at the end of a script to prevent the last result spilling into the console. It's just slightly faster to type than 'halt. Anton.

 [5/6] from: santilli::gabriele::gmail::com at: 7-May-2007 12:52

2007/5/6, Tim Johnson <>:
> I have a need for an "r-expression", that is - a class of functions that > will be evaluated by 'do as part of a block and can have 0 or more
<<quoted lines omitted: 4>>
> 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. :) HTH, Gabriele.

 [6/6] 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]
<<quoted lines omitted: 29>>
> == 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 <> Palmer, Alaska, USA

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