Re: Cannot use ldegree() on symbolic expressions with non-integer exponents

[Martin Helm]

Am Samstag, 27. März 2010 13:37:21 schrieb Jason Lewis:
> I'm still confused about this one. I've searched the web and read the
> documentation. Do I have a fundamental misunderstanding, or is this a
> bug?
> 
> Thanks.
> 
> ---------- Forwarded message ----------
> From: Jason Lewis <address@hidden>
> Date: Wed, 24 Mar 2010 11:52:32 -0400
> Subject: Cannot use ldegree() on symbolic expressions with non-integer
>  exponents To: address@hidden
> 
> I'm a bit confused.  The following code won't work:
> > symbols
> 
> octave-3.2.3.exe:42:C:\Octave\3.2.3_gcc-4.4.0\bin
> 
> > x=sym("x")
> 
> x =
> 
> x
> octave-3.2.3.exe:43:C:\Octave\3.2.3_gcc-4.4.0\bin
> 
> > y=x^2+9
> 
> y =
> 
> 9.0+x^(2.0)
> octave-3.2.3.exe:44:C:\Octave\3.2.3_gcc-4.4.0\bin
> 
> > ldegree(y,x)
> 
> error: power::ldegree(): undefined degree because of non-integer exponent
> octave-3.2.3.exe:44:C:\Octave\3.2.3_gcc-4.4.0\bin
> 
> ...but if I change the input as follows, it works fine:
> > y=x*x+9
> 
> y =
> 
> 9.0+x^2
> octave-3.2.3.exe:45:C:\Octave\3.2.3_gcc-4.4.0\bin
> 
> > ldegree(y,x)
> 
> ans =
> 
> 0.0
> 
> 
> Why does x^2 become x^2.0 and x*x become x^2?  How do I fix this problem?
> 
> Thanks,
> Jason
> _______________________________________________
> Help-octave mailing list
> address@hidden
> https://www-old.cae.wisc.edu/mailman/listinfo/help-octave
> 
I have to say that I don't use the symbolic package so maybe my idea is 
completely worthless.

Did you also try to explicitelyy tell that 2 is an integer, for example

x=sym("x")
y=x^int32(2)+9
ldegree(y,x)

What happens (I can not test it, I do not have the package installed)?

- mh