From help-octave-request at bevo dot che dot wisc dot edu Sat May 24 21:40:52 2003
Subject: product of empty vectors
From: "John W. Eaton" <jwe at bevo dot che dot wisc dot edu>
To: help-octave mailing list <help-octave at bevo dot che dot wisc dot edu>
Cc: Douglas Harder <dwharder at cheetah dot vlsi dot uwaterloo dot ca>
Date: Sat, 24 May 2003 21:40:09 -0500

On 23-May-2003, I wrote:

| On 23-May-2003, Douglas Harder <dwharder at cheetah dot vlsi dot uwaterloo dot ca> wrote:
| 
| | Octave's handling of empty matrices is a little odd:
| | 
| | >> a = 1:2 
| | a =
| |   1  2
| | >> a(1:0)
| | ans = []
| | >> ans * ans'   % this should be 0
| | ans = []
| | >> ans + 3
| | ans = []
| 
| The only real problem here is that Octave interprets 1:0 as a 0x0
| empty matrix instead of a 1x0 empty matrix.  Should we change that?

OK, after a bit of thought, I think we should (if you disagree, please
speak up).  Here is a patch.

Thanks,

jwe


2003-05-24  John W. Eaton  <jwe at bevo dot che dot wisc dot edu>

	* ov-range.cc (try_narrowing_conversion): Convert to [](1x0)
	instead of [](0x0) if range is empty.


Index: src/ov-range.cc
===================================================================
RCS file: /usr/local/cvsroot/octave/src/ov-range.cc,v
retrieving revision 1.28
diff -u -r1.28 ov-range.cc
--- src/ov-range.cc	23 Feb 2003 02:16:53 -0000	1.28
+++ src/ov-range.cc	25 May 2003 02:35:46 -0000
 at @ -71,7 +71,7 @@
       break;
 
     case 0:
-      retval = new octave_matrix (Matrix ());
+      retval = new octave_matrix (Matrix (1, 0));
       break;
 
     default:



-------------------------------------------------------------
Octave is freely available under the terms of the GNU GPL.

Octave's home on the web:  http://www.octave.org
How to fund new projects:  http://www.octave.org/funding.html
Subscription information:  http://www.octave.org/archive.html
-------------------------------------------------------------