I think that could be considered a bug in ginac, or in the wrapping of
ginac in sage.
A workaround that might also speed some things up is to define a
global numerical pi, e.g. "npi = RDF(pi)" and then use npi
everywhere.
-M. Hampton
On Oct 25, 11:13 pm, "Dawes, Andrew M." <da...@pacificu.edu> wrote:
> I have noticed unexpected behavior when trying to take the absolute
> value of a complex exponential (e^{i\theta}). For example, the following
> command fails with "unable to simplify to float approximation":
>
> plot(abs(exp(i*pi*x)),x,0,3)
>
> However, the following gives the correct plot (of constant value 1):
>
> plot(abs(exp(i*float(pi)*x)),x,0,3)
>
> Why does pi need to be a float in order for abs to evaluate it and plot?
> Run outside of the plot function, the abs seems to do the right thing:
>
> abs(exp(i*pi*0))
>
> and
>
> abs(exp(i*pi*3))
>
> both return 1.
>
> I found a related bug ticket (#6926), but I still see this behavior
> despite those bugs being marked fixed. The difference here is the "pi"
> in the exp(). I am running Sage Version 4.5.2 on Mac OS 10.6.4.
>
> Please let me know if I'm doing something wrong or if this should be
> filed as a bug.
>
> Best,
> Andrew Dawes
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