Hi Ladislav,
I was sure I was missing something. Very clever indeed and elegant once one
has got it ! May I respectfully suggest that a little note or comment in
contexts.html would help the reader ?
Patrick
----- Original Message -----
From: "Ladislav Mecir" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Tuesday, March 05, 2002 8:46 AM
Subject: [REBOL] Re: [subject: error and trial]
> Hi Pat,
>
> your code is almost correct, it just omits one special case. See the
> following example:
>
> >> type? a: make error! "my error"
> == error!
> >> u-def? 'a
> == true
> >> undefined? 'a
> == false
>
> Cheers
> L
>
>
> ------------------
> From: "pat665"
> Sent: Monday, March 04, 2002 10:54 PM
> Subject: [REBOL] [subject: error and trial]
>
>
> Hi rebollers,
>
> I am coming again with a question posted on November the 23th 2001. At the
> time, I thought I had understood Ladislav's answer, but the truth is I am
> not so sure.
>
> All began while reading Ladislav's contexts.html...
>
> "There are Words that do not have the ability to refer to Rebol values. We
> can call them undefined Words. [ ...] This function can be used to find
out,
> if a Word is undefined: "
>
> undefined?: func [
> {determines, if a word is undefined}
> word [any-word!]
> ] [
> error? try [error? get/any :word]
> ]
>
> My question was "why use error? two times?". In my eyes, a more simple
> version of the function could be :
>
> u-def?: func [
> {determines, if a word is undefined}
> word [any-word!]
> ] [
> error? try [get/any :word]
> ]
>
> We can test these two functions whith Ladislav's own example of an
undefined
> word.
>
> a-word: first first rebol/words ;== end!
>
> >> undefined? a-word
> == true
> >> u-def? a-word
> == true
>
> >> undefined? 'print
> == false
> >> u-def? 'print
> == false
>
> I am not pretending I am right, because I must be wrong! but I deeply need
> to understand where and why !
>
> Patrick
>
>
> --
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>
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