Path: news.cs.au.dk!not-for-mail
From: "Kasper Østerbye" <kasper@cs.au.dk>
Newsgroups: comp.lang.beta
Subject: Re: Cannot copy NONE?
Date: Wed, 17 Nov 1999 12:34:58 +0100
Organization: University of Aarhus, Department of Computer Science (DAIMI)
Lines: 61
Message-ID: <80u3t2$8m7av$1@xinwen.cs.au.dk>
References: <19991111233439.401.qmail@noatun.mjolner.dk>
NNTP-Posting-Host: xmas.cs.au.dk
X-Trace: xinwen.cs.au.dk 942838498 9117023 255.255.255.255 (17 Nov 1999 11:34:58 GMT)
X-Complaints-To: news@cs.au.dk
NNTP-Posting-Date: 17 Nov 1999 11:34:58 GMT
X-Priority: 3
X-MSMail-Priority: Normal
X-Newsreader: Microsoft Outlook Express 5.00.2314.1300
X-MimeOLE: Produced By Microsoft MimeOLE V5.00.2314.1300
Xref: news.cs.au.dk comp.lang.beta:12165

This is not a Beta specific problem, but common to all languages where a
reference can become none.
The best I can come up with, is to write
t[] -> copy -> u[]
instead of
t.copy -> u[]

the copy pattern can then look like
copy:(# original, copy : ^ Text
enter original[]
do (if original[] = none then
        none -> copy[]
    else
        "make copy of original" -> copy[]
   if)
exit copy[]
#)

-- Kasper

[tricos.com] Sascha Kimmel <kimmel@tricos.com> wrote in message
news:19991111233439.401.qmail@noatun.mjolner.dk...
> Hi!
>
> I found something quite interesting which does not help to generate
> compact code - instead it becomes a bit complicated:
>
> t,u:^text;
> do
> none->t[];
> t.copy->u[];
>
> ***  THIS GIVES A "REFERENCE ***
> *** IS NONE" RUNTIME ERROR !! ***
>
> Well, normally one would not set a text reference to none, but if I read
> some data into an array (^text) and just want to copy the values (not
> the references!) of the corresponding variables into the array (or to
> any other text reference), it is not possible to do this with small code
> if it's possible that there are NONEs in there.
>
> So do I really need to use
>
> (if (t[]<>none)
> then
> t.copy->u[];
> else
> none->u[];
> if);
>
> instead of a small t.copy->u[] ?
>
> Any help is appreciated!
>
> Regards,
> Sascha Kimmel
>
>
>