Dieter Kaiser wrote:
> Hello Ray,
>
> I have finish my calculation to get the complex phase factors for the function
> expintegral_ei. I have used the following relationsship to get the results (see
> the log function on functions.wolfram.com for a reference):
>
> (a) 1/2*(log(z)-log(1/z)) = log(z) for z not in [-inf,0]
> (b) 1/2*(log(z)-log(1/z)) = log(z) - %i*%pi for z in [-inf,0]
>
>
I see I made a mistake in computing 1/2?(log(z)-log(1/z))-log(-z). I
forgot to take the phase term modulo 2*%pi. When I do that, I get the
same answers as you. (This makes a nice little exercise for a complex
variables class!)
This is probably why maxima compute log(-z) incorrectly. It does take
the phase term of -z modulo 2*%pi.
Finally got around to testing your changes. It works nicely now.
Sorry for all the trouble!
Ray