Re: empty ranges are matrices ?

[Jean-Francois Cardoso]

On Mar 29, John W. Eaton wrote:
 > On 29-Mar-2005, Jean-Francois Cardoso <address@hidden> wrote:
 > 
 > | Is it expected behavior that empty ranges have type "matrix" and not
 > | "range"?
 > | 
 > | octave> typeinfo(0:1)
 > | ans = range
 > | octave> typeinfo(1:0)
 > | ans = matrix
 > | octave> size(1:0)
 > | ans =
 > | 
 > |   1  0
 > | 
 > | octave> version
 > | ans = 2.1.67
 > 
 > Yes, the same as it is expected that a range with a single element is
 > converted to a scalar object.  Is this a problem?  How?

It is not a problem that I cannot work around, of course.  But it may
appear counterintuitive: I was disturbed at first that an empty object
cannot be "stacked" freely, in the sense that:

octave> r = 1:-1 ; s = [ r 1  ]
s = 1
octave> r = 1:-1 ; s = [ r ; 1  ]
error: number of columns must match (1 != 0)

while I can do 

octave> vide = zeros(0)  ;
octave> [ vide 1 ]       ;
octave> [ vide ; 1 ]     ;
octave> 

but I now understand that an empty range should be more naturally 
represented as [](1x0) than as [](0x0).  Hence the above error.



But we may have a more serious problem here:

octave> zeros(0)
ans = [](0x0)
octave> zeros([])
warning: zeros (A): use zeros (size (A)) instead
ans = 0
octave> 

Octave does produce a warning, but nothing more.  

Do we really want zeros([]) to return a SCALAR rather than an empty
object?


Best regards, JF



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