Problems with symbolic computation

[Jurgen Defurne]

Hello,

I am using Octave 3.2.4 on Debian 6.0.3. For my thesis I need to use
some .m files from my professor, which use symbolic computation to
obtain filter coefficients. However, when trying to use his programs
I found out that there are some errors.

The following shows a simplified session and the errors I get.

octave:1> symbols
octave:2> x = sym("x")
x =

x
octave:3> H = x^3 + x^2
H =

x^(2.0)+x^(3.0)
octave:4> [a, b] = sym2poly (H)
a =

   1   1   0   0

error: element number 2 undefined in return list
octave:4> H = x^3 + x^2 + x^-1
H =

x^(2.0)+x^(3.0)+x^(-1.0)
octave:5> [a, b] = sym2poly (H)
Please examine your code or adjust this function.
This error may occur because the passed expression is not a polynomial.
error: Reached the set limit (500) for the number of coefficients.
error: called from:
error:   /usr/share/octave/packages/3.2/symbolic-1.0.9/sym2poly.m at line 109, 
column 3
octave:5> 

Regards,

Jurgen