#3401: extend li to work with complex input
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Reporter: was |
Owner: gfurnish
Type: enhancement |
Status: needs_work
Priority: major |
Milestone: sage-4.7.2
Component: calculus |
Keywords: beginner
Work_issues: |
Upstream: N/A
Reviewer: Mike Hansen, Karl-Dieter Crisman, Burcin Erocal |
Author: Michael Yurko
Merged: |
Dependencies:
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Comment(by benjaminfjones):
In #11143 a fully symbolic function is defined for `li(x)` called
`exp_integral_li`, the non-offset logarithmic integral. It would be very
easy to add `Li` by simply returning `exp_integral_li(x) -
exp_integral_li(2)`. On the other hand, adding a symbolic version of `Li`
would be equally easy by copying the definition of `exp_integral_li` and
making one simple change.
If so, what would a good name for the offset `Li` be? Maybe
`exp_integral_li_offset`?
Another thought is that in #11143, we could add an optional parameter
`offset` to the init method for `exp_integral_li` which would return `Li`
instead of `li`. The eval and evalf methods could be bound in the init
call to return the right values and the derivative is obviously the same
for both.
Either of these solutions could be put into #11143 without much effort and
that would take care of the issue in this ticket because evaluation at
complex inputs is handled by mpmath for all the functions defined there.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/3401#comment:14>
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