>
> Yep.  And I'll remark again that
>
>      sum(sqrt(p) for p in primes(1000))
>
> *better* work instantly no matter what we do, or I'm not
> happy with the plan.  And you can't do the above as
> far as I can tell by constructing explicitly a number field
> of degree 2^168.
>
> William

Hmm this seems like a convincing argument for keeping sqrt(p)
and hence also sqrt(-1) symbolic.

Some thoughts

(1) Sage has different types of functions. Symbolic ones (like sin)
and numeric ones like zeta_symmetric. I am strongly convinced that in
order not
to confuse the user numeric functions should make every effort
to convert their arguments to numeric form. I.e. I think
zeta_symmetric(1/2+I) should just work (TM).


(2) Blue sky. Do we need numeric functions at all? Why not keeping
zeta_symmetric symbolic and only make it spit out a value
after applying the N(...) operator. E.g.
sage: zeta_symmetric(1/2+I)
zeta_symmetric(1/2+I)
sage: N(_)
0.485757429670983 - 1.38777878078145e-17*I

This has the advantage that for example

diff(zeta_symmetric(z),z)(1/2+I)

could still have a meaning. After applying N it might attempt
to do numeric differentiation in the point 1/2+I (yes I know this
depends
on zeta_symmetric being holomorphic, it is only an example).


Michel






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