norm, 'fro' - warning: division by zero

[Zbigniew Komarnicki]

Hello,

Please see on this code in octave:
octave-3.0.1 and octave-3.0.2 in Debian lenny.


Here is an example:
=========================
octave:1> A=zeros(5)
A =

   0   0   0   0   0
   0   0   0   0   0
   0   0   0   0   0
   0   0   0   0   0
   0   0   0   0   0

octave:2> norm(A, 'fro')
warning: division by zero
ans = NaN
octave:3>


But when, according to the manual (help norm) write in this way:

>From help system:
P = `"fro"'
          Frobenius norm of A, `sqrt (sum (diag (A' * A)))'.

=========================
octave:5> sqrt (sum (diag (A' * A)))
ans = 0
octave:6>    

Here no warning 'division by zero' and answer is 0 not NaN.

It is a bug in 'norm' implementation or something else?

Thank you, for any comments.

Best wishes,
Zbigniew