#15334: Evaluation of Jacobi elliptic functions for non-real arguments depends
on
previously computed values
-------------------------+-------------------------------------------------
Reporter: | Owner:
davidamadore | Status: new
Type: defect | Milestone: sage-5.13
Priority: major | Keywords: special function elliptic
Component: numerical | integral jacobi
Merged in: | Authors:
Reviewers: | Report Upstream: N/A
Work issues: | Branch:
Commit: | Dependencies:
Stopgaps: |
-------------------------+-------------------------------------------------
The following example shows that numerically evaluating sn(I,1/2) first
fails ("cannot evaluate symbolic expression numerically") and then
succeeds once the value sc(1,1/2) has been computed:
{{{
sage: N(jacobi("sn", I, 1/2))
---------------------------------------------------------------------------
TypeError Traceback (most recent call
last)
<ipython-input-1-e0000742d9d6> in <module>()
----> 1 N(jacobi("sn", I, Integer(1)/Integer(2)))
/usr/src/local/sage-5.12/local/lib/python2.7/site-
packages/sage/misc/functional.pyc in numerical_approx(x, prec, digits)
1395 prec = int((digits+1) * LOG_TEN_TWO_PLUS_EPSILON) + 1
1396 try:
-> 1397 return x._numerical_approx(prec)
1398 except AttributeError:
1399 from sage.rings.complex_double import
is_ComplexDoubleElement
/usr/src/local/sage-5.12/local/lib/python2.7/site-
packages/sage/symbolic/expression.so in
sage.symbolic.expression.Expression._numerical_approx
(sage/symbolic/expression.cpp:22615)()
TypeError: cannot evaluate symbolic expression numerically
sage: N(jacobi("sc", 1, 1/2))
1.34737147138542
sage: N(jacobi("sn", I, 1/2))
1.34737147138542*I
}}}
(in fact, evaluating sc with any arguments whatsoever seems to make the sn
function work afterward).
--
Ticket URL: <http://trac.sagemath.org/ticket/15334>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
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