Re: Why is 4+ legal?

Oh, I did not know +/- postscripts signify a double number. I had never
seen that documented, nor did I understand that from Leon's answer. Now
that I know about it, I will have frequent use for it. I wonder what else I
am missing. What references document standard Forth? None of my Forth books
mention this particular definition, including the SwiftX documents, as far
as I can tell.

Thanks,
David Graham

> -----Original Message-----
> From: swiftx-bounce_at_forth.com [mailto:swiftx-bounce_at_forth.com]On Behalf
> Of Appert, Kevin
> Sent: Friday, June 01, 2001 9:14 AM
> To: 'swiftx_at_forth.com'
> Subject: [swiftx] Re: Why is 4+ legal?
>
>
>
> To deal with the ED class of problem on one project we had a
> rule that
> numbers had to start with 0, like 0ED and NOTHING ELSE could
> start with a 0.
> The first few integers 00, 01, 02, etc. were defined and the 0, 1 and 2
> definitions removed. This caused problems for one of my
> colleagues who was
> just learning C and carried the habit over where he learned what C thought
> 0321 meant the hard way. This was a system which only had HEX and DECIMAL
> and no $ flag for hex numbers.
> You can't always tell the customer what he's doing wrong or
> change the
> standard to avoid all awkwardness. ED frequently starts the editor and I
> guess $ED could be some sort of editor string. Perhaps all hex numbers
> should start with $ and NOTHING ELSE should.
> So 1+ is an increment and 4+ is a double number. 2+ is a coin toss
> which caught me a while back when I didn't see it in some great code Leon
> wrote. Maybe we should take + off the list of double number flags. Has
> anyone ever used it or seen it used?
>
> > ----------
> > From: David Graham[SMTP:dgraham_at_GrahamAutomationInc.com]
> > Reply To: swiftx_at_forth.com
> > Sent: Wednesday, May 30, 2001 12:25 PM
> > To: swiftx_at_forth.com
> > Subject: [swiftx] Re: Why is 4+ legal?
> >
> >
> > I wanted to report a peculiar feature of SwiftX 3.0, HC12
> > version. The compiler accepts n+ or n-, where n is any numeric
> > digit, as a legal definition, and leaves n 0 in the stack. I
> just caught
> > by
> > this when I mistyped 4 + as 4+.
> >
> > Regards,
> > David Graham
> > Graham Automation, Inc.
> > PO Box 623
> > McMinnville, OR 97128
> > (503) 434-8636 Fax (503) 212-0181
> > dgraham_at_GrahamAutomationInc.com
> >
> >
> > > Hi David,
> > >
> > > That's an artifact of the standard Forth double number conversion.
> > Always
> > > be very careful with anything that might accidentally be
> converted to a
> > > number! One of our competitor's systems defines two words, ED
> > > and $ED which
> > > conflict with hex numbers of the same value. Drives me crazy.
> > >
> > > Leon

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Received on Fri Jun 01 2001 - 10:03:57 PDT