Wrong simplification of log(1/z)



On 7/29/08, Dieter Kaiser <drdieterkaiser at web.de> wrote:

>  O.k., I have tried to implement plog to get the correct phase factors in the
>  transformations. But plog is very annoying. I don't get it silent. I try to
>  declare almost everything to be complex, but it still continue to ask the
>  useless question: Is "THIS" positive or negative?

Well, that is certainly frustrating. I'm guessing that these questions
originate from carg, cabs, imagpart, and/or realpart, not plog itself.
I am in favor of making those 4 functions less vocal.

>  I had again a look at the Log function. I think log(1/z) -> -log(z) is really a
>  bug.

Agreed, it really is a bug.

>  There is no reason to do the wrong simplification for log(1/z). It my opinion
>  there is also no reason to do the simplification log(a/b)->log(a)-log(b) when we
>  are not sure that a,b are real or complex and not negative real.

Agreed, Maxima should never make unjustified simplifications.

best

Robert Dodier