[REBOL] Re: No return Value???
From: tim:johnsons-web at: 28-Nov-2003 11:50
* Maxim Olivier-Adlhoch <[maximo--meteorstudios--com]> [031128 11:41]:
> print does not return any value,
Yeah, I know, I will probable have to use a tmp word,
test it and use a default return value.
> I had to work around that in encompass... (hence the /silent refinement)
>
> you can build up a function which returns no value:
>
> a: func [data][
> ; do what you want with data
> return unset 'data
> ]
>
> the above is not really usefull but if you want to free the memory used up by data
(cause each word in a function keeps its value in between each function call), then this
is one way of ensuring it does not hang around.
>
> ladislav and gabrielle might correct me if I'm wrong.
>
> -MAx
> ---
> "You can either be part of the problem or part of the solution, but in the end, being
part of the problem is much more fun."
>
> > -----Original Message-----
> > From: Tim Johnson [mailto:[tim--johnsons-web--com]]
> > Sent: Friday, November 28, 2003 2:38 PM
> > To: [rebol-list--rebol--com]
> > Cc: [apwing--zonnet--nl]
> > Subject: [REBOL] No return Value???
> >
> >
> >
> > Hello Rebols:
> > I've got a question:
> > I've written a function called 'fetch, which has print
> > stubs to help follow the flow control.
> >
> > If you evaluate 'print with 'fetch, no value is
> > returned.
> >
> > Can someone tell me why this is so?
> > TIA
> > tim
> >
> > (example and code follows)
> > Example:
> > >> do %test-fetch.r
> > Script: "Untitled" (none)
> > >> fetch 'abc
> > type = 'word
> > val is unset
> > returning unset words as default value
> > == none
> > >> fetch 'print
> > type = 'word
> > val is set
> >
> > The code for 'fetch and helper function 'safe-reduce
> > follows:
> > REBOL[]
> > ;
> > --------------------------------------------------------------
> > -----------------
> > make object! [
> > default-value: none
> > set 'fetch func[ {safe data retrieval. Handles any value}
> > val [any-type!]
> > /seed {set default value} /deep {If block, reduce}
> > /same {If unset return 'val}
> > /local tmp][
> > either word? val[
> > print "type = 'word"
> > either value? val[
> > print "val is set"
> > get val
> > ][
> > print "val is unset"
> > either same[
> > print "returning unset
> > word as the word"
> > val
> > ][
> > print "returning unset
> > words as default value"
> > default-value
> > ]
> > ]
> > ][ ; any other type but 'word
> > print ["type = " (type? val)]
> > either block? val[
> > either deep[
> > safe-reduce/deep val
> > ][
> > safe-reduce val
> > ]
> > ][
> > val
> > ]
> > ]
> > ]
> > ]
> > ;
> > --------------------------------------------------------------
> > -----------------
> > safe-reduce: function[blk[block!] {reduce block, leaving unset values}
> > /deep {reduce nested blocks} ][rblk _reduce][
> > dummy: func[val /deep][val] ; pass
> > ; below a function assignment using the prefix colon
> > _reduce: either deep[:safe-reduce][:dummy]
> > ; since 'reduce is a native value (compiled into binary)
> > ; try it first
> > either all[(not deep) (rblk: attempt[reduce blk])][
> > print "Used native 'reduce"
> > rblk
> > ][
> > print "Block with unset values, using 'safe-reduce"
> > rblk: make block! length? blk
> > foreach element blk[
> > either word? element[
> > either value? element[
> > append rblk (get element)
> > ][
> > append rblk element
> > ]
> > ][
> > either block? element[
> > append/only rblk
> > _reduce/deep element
> > ][
> > append rblk element
> > ]
> > ]
> > ]
> > rblk
> > ]
> > ]
> > --
> > Tim Johnson <[tim--johnsons-web--com]>
> > http://www.alaska-internet-solutions.com
> > --
> > To unsubscribe from this list, just send an email to
> > [rebol-request--rebol--com] with unsubscribe as the subject.
> >
> >
>
> --
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--
Tim Johnson <[tim--johnsons-web--com]>
http://www.alaska-internet-solutions.com
